Radiation-sensitive resin composition and method for forming resist pattern

ABSTRACT

A radiation-sensitive resin composition includes: a resin including a structure unit having an acid-dissociable group; a radiation-sensitive acid generator; and a solvent. The radiation-sensitive acid generator includes at least two of compounds represented by formulae (1) to (3), provided that the compound represented by formula (1) and the compound represented by formula (3) within the scope of the compound represented by formula (2) are excluded. In the formulae (1) to (3), R 1 , R 2  and R 3  are each independently a group having a cyclic structure; X 11 , X 12 , X 21 , X 22 , X 31  and X 32  are each independently a hydrogen atom, a fluorine atom, or a fluorinated hydrocarbon group, provided that both X 11  and X 12 , both X 21  and X 22 , and both X 31  and X 32  are not a hydrogen atom, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent ApplicationNo. 2017-081633, filed Apr. 17, 2017, and to Japanese Patent ApplicationNo. 2018-056288, filed Mar. 23, 2018. The contents of these applicationsare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a radiation-sensitive resin compositionand a method for forming a resist pattern.

Description of the Related Art

A photolithography technology using a resist composition has been usedfor the fine circuit formation in a semiconductor device. As therepresentative procedure, for example, a resist pattern is formed on asubstrate by generating an acid by irradiating the coating of the resistcomposition with a radioactive ray through a mask pattern, and thenreacting in the presence of the acid as a catalyst to generate thedifference of solubility of a resin into an alkaline or organicdeveloper between an exposed part and a non-exposed part.

In the photolithography technology, the micronization of the pattern ispromoted by using a short wave length radioactive ray such as ArFexcimer laser, and by using immersion exposure method (liquid immersionlithography) in which the exposure is carried out in a liquid mediumfilled in the space between a lens of an exposing apparatus and a resistfilm. As a next generation technology, a lithography using a short wavelength such as an electron beam, X ray and EUV (extreme ultraviolet ray)has been studied.

With progress of the exposing technology, studies of a photoacidgenerator and the like, a major ingredient of the resist composition,are attempted for the purpose of improving the sensitivity andresolution of the resist composition. As the resist composition having apattern resolution from micron size to submicron size, proposed is aphotosensitive composition including a hydroxystyrene-based polymerhaving high plasma etching resistance and a photoacid generator having acarbon atom connected to a sulfonate group as a secondary carbon or atertiary carbon (Patent Document 1). However, in ArF generation, sincethe absorption of the radioactive ray for exposing in the aromaticstructure of the hydroxystyrene-based polymer becomes too strong, it isdifficult to form a desired fine shape of pattern.

Therefore, there has been used a resin having an alicyclic structurehaving weak absorption as a protecting group in place of thehydroxystyrene-based polymer. However, the photoacid generator used incombination of the hydroxystyrene-based polymer have no sufficient acidintensity in order to proceed the deprotection of the resin having analicyclic structure.

Therefore, an acid generator in which a carbon proximal to the sulfonategroup is substituted with a fluorine is implemented, as a photoacidgenerator resulting in an acid having a sufficient acid intensity forthe deprotection (Patent Documents 2 to 4).

PRIOR ART DOCUMENT Patent Document

-   [Patent Document 1] JP-A-10-10715-   [Patent Document 2] JP-A-2002-214774-   [Patent Document 3] JP-A-2004-002252-   [Patent Document 4] International Patent Publication No. WO    2008/099869

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Recently, as the micronization of the resist pattern is proceeding,Critical Dimension Uniformity (CDU) properties which is an index of theuniformity of a line width and a hole diameter, Mask Error EnhancementFactor (MEEF) properties which is an amount of change in the line widthand the hole diameter corresponding to the amount of change in a masksize, Line Width Roughness (LWR) properties which shows a variation ofthe line width of the resist pattern, and the like are required, andvarious resist properties are required to be further improved. However,in the radiation-sensitive resin composition including the acidgenerator, all properties are not obtained at a sufficient level.

An object of the present invention is to provide a radiation-sensitiveresin composition being capable of providing CDU, MEEF, and LWRproperties at sufficient levels even if a next generation exposingtechnology is applied, and to provide a method for forming a resistpattern.

SUMMARY OF THE INVENTION

As a result of intensive studies for solving these issues, the inventorshave found that the object could be accomplished by using a combinationof a plurality of acid generators having certain structures, whilevarious resist properties could not be provided by using only oneradiation-sensitive acid generator.

The present invention relates to a radiation-sensitive resincomposition, including:

a resin including a structure unit having an acid-dissociable group;

a radiation-sensitive acid generator; and

a solvent;

wherein the radiation-sensitive acid generator includes at least two ofcompounds represented by the following formulae (1) to (3), providedthat the compound represented by the formula (1) and the compoundrepresented by the formula (3) within the scope of the compoundrepresented by the formula (2) are excluded:

(In the formulae (1) to (3),

R¹, R² and R³ are each independently a group having a cyclic structure;

X¹¹, X¹², X²¹, X²², X³¹ and X³² are each independently a hydrogen atom,a fluorine atom, or a fluorinated hydrocarbon group, provided that bothX¹¹ and X¹², both X²¹ and X²², and both X³¹ and X³² are not a hydrogenatom, respectively;

A¹¹, A¹², A²¹, A²², A³¹ and A³² are each independently a hydrogen atom,or a hydrocarbon group having a carbon number of 1 to 20;

m¹, m² and m³ are each independently an integer of 0 to 5;

n¹, n² and n³ are each independently an integer of 1 to 4;

G is a single bond, or a divalent linking group; and

Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ are each independently a monovalent onium cation.)

The radiation-sensitive resin composition includes at least two ofcompounds represented by the above formulae (1) to (3) (hereinafter,also referred respectively as a “compound (1)”, for example) as theradiation-sensitive acid generator. Therefore, the composition canprovide all of CDU, MEEF and LWR properties at sufficient levels.Although the reason is not clear, it is presumed that the acid diffusionlength and the acidity are optimized as a whole synergistically oradditively by using a plurality of certain radiation-sensitive acidgenerators, and thereby various resist properties are improved.

Preferably, the compound represented by the above formula (1) is acompound represented by the following formula (1′), the compoundrepresented by the above formula (2) is a compound represented by thefollowing formula (2′), and the compound represented by the aboveformula (3) is a compound represented by the following formula (3′):

(In the formulae (1′) to (3′),

R^(1a), R^(2a) and R^(3a) are each independently a substituted orunsubstituted alicyclic group;

X¹¹, X¹², X²¹, X²², X³¹ and X³² are each independently a fluorine atom,or a monovalent fluorinated chain hydrocarbon group having a carbonnumber of 1 to 10;

A²¹, A²², A³¹ and A³² are each independently a hydrogen atom, or a chainhydrocarbon group having a carbon number of 1 to 10;

m^(2a) and m^(3a) are each independently 0 or 1;

n^(1a), n^(2a) and n^(3a) are each independently 1 or 2;

G has the same meaning as in the above formula (1); and

Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ have the same meaning as in the above formulae (1)to (3), respectively.)

The radiation-sensitive resin composition can effectively provide CDU,MEEF and LWR properties at higher level by including at least two ofcompounds represented by the above formulae (1′) to (3′) as theradiation-sensitive acid generator.

Preferably, the radiation-sensitive acid generator is:

the compound represented by the above formula (1) and the compoundrepresented by the above formula (2);

the compound represented by the above formula (1) and the compoundrepresented by the above formula (3); or

the compound represented by the above formula (1), the compoundrepresented by the above formula (2) and the compound represented by theabove formula (3).

The various resist properties can be further improved by including atleast one of the compounds (2) and (3) as the radiation-sensitive acidgenerator in addition to the compound (1).

When at least one of the compounds (2) and (3) is included as theradiation-sensitive acid generator in addition to the compound (1), acontent of the compound represented by the above formula (1) ispreferably not less than 1 part by mass and not more than 45 parts bymass based on 100 parts by mass of the resin. Thereby, the variousresist properties can be improved effectively.

Preferably, each of a molecular weight of an anionic moiety in theradiation-sensitive acid generator is 230 or more. Thereby, it ispossible to control the diffusion length of an acid generated from theradiation-sensitive acid generator to the suitable range, and providevarious resist properties at higher level.

Preferably, the radiation-sensitive resin composition further includesan acid diffusion controlling agent. Accordingly, it is possible toimprove the contrast between an exposed part and a non-exposed part, andthereby further improve various resist properties.

Preferably, the acid diffusion controlling agent is aradiation-sensitive weak acid generator that generates an acid incapableof inducing dissociation of the acid-dissociable group in a conditionthat an acid generated by the radiation-sensitive acid generatordissociates the acid-dissociable group.

The present invention also relates to a method of forming a resistpattern, including the steps of:

forming a resist film from the radiation-sensitive resin composition;

exposing the resist film; and

developing the exposed resist film.

According to the method of forming a resist pattern, a high-qualityresist pattern can be formed effectively because of using theradiation-sensitive resin composition having improved various resistproperties.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

<Radiation-Sensitive Resin Composition>

The radiation-sensitive resin composition according to the presentembodiment (hereinafter, also referred simply as a “composition”)includes a resin, a radiation-sensitive acid generator, and a solvent.The composition may also include an optional ingredient as long as theeffect of the present invention is not impaired.

(Resin)

The resin is an aggregation of polymers, each polymer including astructure unit having an acid-dissociable group (hereinafter, alsoreferred as a “structure unit (I)”). (Hereinafter, the resin is alsoreferred as a “base resin”.) The “acid-dissociable group” refers to asubstituent group with which a hydrogen atom in a group such as acarboxy group, a phenolic hydroxide group, an alcoholic hydroxide group,and a sulfo group is substituted, and the acid-dissociable group isdissociated by an acid. The radiation-sensitive resin compositionprovides an improved patternability because of the resin including thestructure unit (I).

Preferably, the base resin includes a structure unit (II) in addition tothe structure unit (I), the structure unit (II) including at least oneselected from the group consisting of a lactone structure, a cycliccarbonate structure and a sultone structure as described below. The baseresin may include any other structure unit other than the structure unit(I) and the structure unit (II). Each of the structure units will now bedescribed.

[Structure Unit (I)]

The structure unit (I) is a structure unit having an acid-dissociablegroup. The structure unit (I) is not particularly limited as long as theunit has an acid-dissociable group. Examples of the structure unit (I)include a structure unit having a tertiary alkyl ester moiety; astructure unit having a structure in which a hydrogen atom in a phenolichydroxide group is substituted with a tertiary alkyl group; and astructure unit having an acetal bond. In terms of improving thepatternability of the radiation-sensitive resin composition, thestructure unit (I) is preferably a structure unit represented by thefollowing formula (2) (hereinafter, also referred to a “structure unit(I-1)”).

In the above formula (2), R⁷ is a hydrogen atom, a fluorine atom, amethyl group, or a trifluoromethyl group; R⁸ is a hydrogen atom, or amonovalent hydrocarbon group having a carbon number of 1 to 20; R⁹ andR¹⁰ are each independently a monovalent chain hydrocarbon group having acarbon number of 1 to 10, or a monovalent alicyclic hydrocarbon grouphaving a carbon number of 3 to 20, or represent a divalent alicyclicgroup having a carbon number of 3 to 20, which is obtained by combiningR⁹ and R¹⁰ with the carbon atom to which they are bound; L¹ represents asingle bond, or a divalent linking group. However, when L¹ is thedivalent linking group, a carbon atom which is bound to an oxygen atomof —COO— in the above formula (2) is a tertiary carbon, or its structureat the terminal side of the side chain is —COO—.

As R⁷ described above, in terms of the copolymerizability of monomersresulting in the structure unit (I-1), a hydrogen atom or a methyl groupis preferred. A methyl group is more preferred.

Examples of the monovalent hydrocarbon group having a carbon number of 1to 20 represented by R⁸ as described above include a chain hydrocarbongroup having a carbon number of 1 to 10, a monovalent alicyclichydrocarbon group having a carbon number of 3 to 20, and a monovalentaromatic hydrocarbon group having a carbon number of 6 to 20.

Examples of the chain hydrocarbon group having a carbon number of 1 to10 represented by R⁸ to R¹⁰ as described above include a straight orbranched chain saturated hydrocarbon group having a carbon number of 1to 10, or a straight or branched chain unsaturated hydrocarbon grouphaving a carbon number of 1 to 10.

Examples of the alicyclic a hydrocarbon group having a carbon number of3 to 20 represented by R⁸ to R¹⁰ as described above include a monocyclicor polycyclic saturated hydrocarbon group, or a monocyclic or polycyclicunsaturated hydrocarbon group. Preferred examples of the monocyclicsaturated hydrocarbon group include a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, and a cyclooctyl group. Preferred examplesof the polycyclic cycloalkyl group include a bridged alicyclichydrocarbon group including a norbornyl group, an adamantyl group, atricyclodecyl group, and a tetracyclododecyl group. The bridgedalicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbongroup in which non-adjacent two carbon atoms of the alicyclic ring arebonded together via a binding chain having one or more carbon atoms.

Examples of the monovalent aromatic hydrocarbon group having a carbonnumber of 6 to 20 represented by R⁸ as described above include an arylgroup including a phenyl group, a tolyl group, a xylyl group, a naphthylgroup, and an anthryl group; and an aralkyl group including a benzylgroup, a phenethyl group, and a naphthyl methyl group.

Preferred examples of R⁸ include a straight or branched chain saturatedhydrocarbon group having a carbon number of 1 to 10, and an alicyclichydrocarbon group having a carbon number of 3 to 20.

The divalent alicyclic group having a carbon number of 3 to 20, which isobtained by combining a combination of the chain hydrocarbon group orthe alicyclic hydrocarbon group represented by R⁹ and R¹⁰ with thecarbon atom to which they are bound, is not particularly limited as longas the group is a group obtained by removing two hydrogen atoms from thesame carbon atom of a monocyclic or polycyclic alicyclic hydrocarboncarbocyclic ring having the same number of carbon atoms as describedabove. The group may be a monocyclic hydrocarbon group or a polycyclichydrocarbon group. The polycyclic hydrocarbon group may be a bridgedalicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, andmay be a saturated hydrocarbon group or an unsaturated hydrocarbongroup. The fused alicyclic hydrocarbon group refers to a polycyclicalicyclic hydrocarbon group in which a plurality of alicyclic ringsshares one side (a bond between adjacent two carbon atoms).

Preferred examples of the saturated hydrocarbon group in the monocyclicalicyclic hydrocarbon group include a cyclopentanediyl group, acyclohexanediyl group, a cycloheptanediyl group, and a cyclooctanediylgroup. Preferred examples of the unsaturated hydrocarbon group include acyclopentenediyl group, a cyclohexenediyl group, a cycloheptenediylgroup, a cyclooctenediyl group, and a cyclodecenediyl group. Preferredexamples of the polycyclic alicyclic hydrocarbon group include a bridgedalicyclic saturated hydrocarbon group. For example, a group such as abicyclo[2.2.1]heptan-2,2-diyl group (a norbornane-2,2-diyl group), abicyclo[2.2.2]octan-2,2-diyl group, or atricyclo[3.3.1.1^(3,7)]decan-2,2-diyl group (an adamantane-2,2-diylgroup) is preferred.

Examples of the divalent linking group represented by L¹ as describedabove include an alkanediyl group, a cycloalkanediyl group, analkenediyl group, *—R^(LA)O—, and —R^(LB)COO—. (* refers to a bond tothe side of oxygen.) However, when the group is other than —R^(LB)COO—,the carbon atom connecting to the oxygen atom of —COO— in the aboveformula (2) is a tertiary carbon, and the carbon atom does not have anyhydrogen atom. The tertiary carbon is obtained when there are two bondsfrom the same carbon atom in the group, or when one or two substituentgroups are further connected to the carbon atom having one of the bondsin the group. A part of or all of hydrogen atoms in the group may besubstituted with a halogen atom including a fluorine atom or chlorineatom, or a cyano group.

The alkanediyl group is preferably an alkanediyl group having a carbonnumber of 1 to 8.

Examples of the cycloalkanediyl group include a monocycliccycloalkanediyl group including a cyclopentanediyl group and acyclohexanediyl group; and a polycyclic cycloalkanediyl group includinga norbornanediyl group and an adamantanediyl group. The cycloalkanediylgroup is preferably a cycloalkanediyl group having a carbon number of 5to 12.

Examples of the alkenediyl group include an ethenediyl group, apropenediyl group, and a butenediyl group. The alkenediyl group ispreferably an alkenediyl group having a carbon number of 2 to 6.

Examples of R^(LA) in the *—R^(LA)O— include the alkanediyl group, thecycloalkanediyl group, and the alkenediyl group as each described above.Examples of R^(LB) in *—R^(LB)COO— include the alkanediyl group, thecycloalkanediyl group, and the alkenediyl group as each described above,and an arenediyl group. Examples of the arenediyl group include aphenylene group, a tolylene group, and a naphthylene group. Thearenediyl group is preferably an arenediyl group having a carbon numberof 6 to 15.

Among them, preferably, R⁸ is an alkyl group having a carbon number of 1to 4, and R⁹ and R¹⁰ are a monocyclic or polycyclic cycloalkanestructure in which the alicyclic structure is obtained by combining R⁹and R¹⁰ with the carbon atom to which they are bound. Preferably, L is asingle bond or *—R^(LA)O—. Preferred R^(LA) is an alkanediyl group.

Examples of the structure unit (I-1) include structure units representedby the following formulae (3-1) to (3-4) (hereinafter, also referred as“structure unit (I-1-1) to (I-1-4)”).

In the above formulae (3-1) to (3-4), R⁷ to R¹⁰ have the same meaning asin the above formula (2); and i and j are each independently an integerof 1 to 4. n_(A) is 0 or 1.

i and j are preferably 1. R⁸ to R¹⁰ are preferably a methyl group, anethyl group, or an iso-propyl group.

Among them, the structure unit (I-1) is preferably the structure unit(I-1-1) or the structure unit (I-1-2), more preferably a structure unithaving a cyclopentane structure or a structure unit having an adamantanestructure, further preferably a structure unit derived from1-alkylcyclopentyl (meth)acrylate, a structure unit derived from2-alkyladamantyl (meth)acrylate, and particularly preferably a structureunit derived from 1-methylcyclohexyl (meth)acrylate or a structure unitderived from 2-ethyladamantyl (meth)acrylate.

The base resin may include one type of the structure unit (I), or two ormore types of the structure units (I) in combination.

The lower limit of the content by percent of the structure unit (I) ispreferably 10 mol %, more preferably 15 mol %, further preferably 20 mol%, and more further preferably 30 mol % based on the total structureunits as the component of the base resin. The upper limit of the contentby percent is preferably 90 mol %, more preferably 80 mol %, furtherpreferably 75 mol %, and particularly preferably 70 mol %. By adjustingthe content by percent of the structure unit (I) within the ranges, thepatternability of the radiation-sensitive resin composition can befurther improved.

[Structure Unit (II)]

The structure unit (II) is a structure unit including at least oneselected from the group consisting of a lactone structure, a cycliccarbonate structure and a sultone structure. The solubility of the baseresin into a developer can be adjusted by further introducing thestructure unit (II). As a result, the radiation-sensitive resincomposition can provide improved lithography properties such as theresolution. The adhesion between a resist pattern formed from the baseresin and a substrate can also be improved.

Examples of the structure unit (II) include structure units representedby the following formulae (T-1) to (T-10)

In the above formulae, R^(L1) is a hydrogen atom, a fluorine atom, amethyl group, or a trifluoromethyl group; R^(L2) to R^(L5) are eachindependently a hydrogen atom, an alkyl group having a carbon number of1 to 4, a cyano group, a trifluoromethyl group, a methoxy group, amethoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or adimethylamino group; R^(L4) and R^(L5) may be a divalent alicyclic grouphaving a carbon number of 3 to 8, which is obtained by combining R^(L4)and R^(L5) with the carbon atom to which they are bound. L² is a singlebond, or a divalent linking group; X is an oxygen atom or a methylenegroup; k is an integer of 0 to 3; and m is an integer of 1 to 3.

Example of the divalent alicyclic group having a carbon number of 3 to8, which is composed of a combination of R^(L4) and R^(L5) with thecarbon atom to which they are bound, includes the divalent alicyclicgroup having a carbon number of 3 to 8 in the divalent alicyclic grouphaving a carbon number of 3 to 20, which is composed of a combination ofthe chain hydrocarbon group or the alicyclic hydrocarbon grouprepresented by R⁹ and R¹⁰ in the above formula (2) with the carbon atomto which they are bound. One or more hydrogen atoms on the alicyclicgroup may be substituted with a hydroxy group.

Examples of the divalent linking group represented by L² as describedabove include a divalent straight or branched chain hydrocarbon grouphaving a carbon number of 1 to 10; a divalent alicyclic hydrocarbongroup having a carbon number of 4 to 12; and a group composed of one ormore of the hydrocarbon group thereof and at least one group of —CO—,—O—, —NH— and —S—.

Among them, the structure unit (II) is preferably a group having alactone structure, more preferably a group having a norbornane lactonestructure, and further preferably a group derived from a norbornanelactone-yl (meth)acrylate.

The lower limit of the content by percent of the structure unit (II) ispreferably 20 mol %, more preferably 25 mol %, and further preferably 30mol % based on the total structure units as the component of the baseresin. The upper limit of the content by percent is preferably 80 mol %,more preferably 70 mol %, and further preferably 60 mol %. By adjustingthe content by percent of the structure unit (II) within the ranges, theradiation-sensitive resin composition can provide improved lithographyproperties such as the resolution.

The adhesion between the formed resist pattern and the substrate canalso be improved.

[Other Structure Unit]

The base resin may also include any other structure unit in addition tothe structure units (I) and (II). Example of the other structure unitincludes a structure unit having a polar group, provided that thestructure unit within the scope of the structure unit (II) is excluded.The base resin can adjust its solubility into the developer by furtherincluding the structure unit having a polar group in the resin. As aresult, the radiation-sensitive resin composition can provide improvedlithography properties such as the resolution. Examples of the polargroup include a hydroxy group, a carboxy group, a cyano group, a nitrogroup, and a sulfonamide group. Among them, a hydroxy group or a carboxygroup is preferred, and a hydroxy group is more preferred.

Example of the structure unit having a polar group includes structureunits represented by the following formulae.

In the above formulae, R^(A) is a hydrogen atom, a fluorine atom, amethyl group, or a trifluoromethyl group.

When the base resin includes the structure unit having a polar group,the lower limit of the content by percent of the structure unit having apolar group is preferably 5 mol %, more preferably 10 mol %, and furtherpreferably 20 mol % based on the total structure units as the componentof the base resin. The upper limit of the content by percent ispreferably 90 mol %, more preferably 80 mol %, and further preferably 70mol %. By adjusting the content by percent of the structure unit havinga polar group within the ranges, the radiation-sensitive resincomposition can provide improved lithography properties such as theresolution.

The base resin may also include a structure unit derived from ahydroxystyrene (hereinafter, also referred as a “structure unit (III)”)as the other structure unit in addition to the structure unit having apolar group. The structure unit (III) contributes to the improvement ofthe etching resistance and the improvement of the difference insolubility into the developer between the exposed part and thenon-exposed part (solubility contrast). In particular, the resin can besuitably applied for a pattern formation by exposing to radiation havinga wavelength of 50 nm or less, for example, an electron beam or EUV. Inthis case, the resin has preferably the structure unit (I) and thestructure unit (III).

However, the polymerization of the hydroxystyrene is inhibited by theeffect of its phenolic hydroxide group. Therefore, hydroxystyrene ispolymerized in a state that the phenolic hydroxide group is preferablyprotected with a protecting group such as an alkali-dissociable group,and then hydrolyzed for the deprotection of the phenolic hydroxide groupto obtain the structure unit (III). The structure unit from which thestructure unit (III) is obtained by the hydrolysis is preferablyrepresented by the following formula (4).

In the above formula (4), R¹¹ is a hydrogen atom, a fluorine atom, amethyl group, or a trifluoromethyl group; R¹² is a monovalenthydrocarbon group having a carbon number of 1 to 20, or an alkoxy group.Example of the monovalent hydrocarbon group having a carbon number of 1to 20 of R¹² includes the monovalent hydrocarbon group having a carbonnumber of 1 to 20 of R⁸ in the structure unit (I). Examples of thealkoxy group include a methoxy group, an ethoxy group and a tert-butoxygroup.

Preferred R¹² is an alkyl group and an alkoxy group. A methyl group or atert-butoxy group is more preferred.

When the resin is for exposing to radiation having a wavelength of 50 nmor less, the lower limit of the content by percent of the structure unit(III) is preferably 20 mol %, and more preferably 30 mol % based on thetotal structure units as the component of the resin. The upper limit ofthe content by percent is preferably 80 mol %, and more preferably 70mol %.

(Synthesis Method of Base Resin)

For example, the base resin can be synthesized by polymerizing eachmonomer for providing each structure unit with a radical polymerizationinitiator or the like in a suitable solvent.

Examples of the radical polymerization initiator include an azo-basedradical initiator, including azobisisobutyronitrile (AIBN),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2-cyclopropylpropanenitrile),2,2′-azobis(2,4-dimethylvaleronitrile), and dimethyl2,2′-azobisisobutyrate; and peroxide-based radical initiator, includingbenzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Amongthem, AIBN or dimethyl 2,2′-azobisisobutyrate is preferred, and AIBN ismore preferred. The radical initiator may be used alone, or two or moreradical initiators may be used in combination.

Examples of the solvent used for the polymerization include

alkanes including n-pentane, n-hexane, n-heptane, n-octane, n-nonane,and n-decane;

cycloalkanes including cyclohexane, cycloheptane, cyclooctane, decalin,and norbornane;

aromatic hydrocarbons including benzene, toluene, xylene, ethylbenzene,and cumene;

halogenated hydrocarbons including chlorobutanes, bromohexanes,dichloroethanes, hexamethylenedibromide, and chlorobenzenes;

saturated carboxylate esters, including ethyl acetate, n-butyl acetate,i-butyl acetate, and methyl propionate;

ketones including acetone, methyl ethylketone, 4-methyl-2-pentanone, and2-heptanone;

ethers including tetrahydrofuran, dimethoxyethanes, and diethoxyethanes;and

alcohols including methanol, ethanol, 1-propanol, 2-propanol, and4-methyl-2-pentanol. The solvent used for the polymerization may be usedalone, or two or more solvents may be used in combination.

The reaction temperature of the polymerization is typically from 40° C.to 150° C., and preferably from 50° C. to 120° C. The reaction time istypically from 1 hour to 48 hours, and preferably from 1 hour to 24hours.

Although the molecular weight of the base resin is not particularlylimited, the weight average molecular weight (Mw) is preferably not lessthan 1,000 and not more than 50,000, more preferably not less than 2,000and not more than 30,000, further preferably not less than 3,000 and notmore than 15,000, and particularly preferably not less than 4,000 andnot more than 12,000, as determined by Gel Permeation Chromatography(GPC) relative to standard polystyrene. If the Mw of the base resin isbelow the lower limits, the thermal resistance of the resulting resistfilm may be decreased. If the Mw of the base resin is beyond the upperlimits, the developability of the resist film may be decreased.

For the base resin, the ratio of Mw to the number average molecularweight (Mn) as determined by GPC relative to standard polystyrene(Mw/Mn) is typically not less than 1 and not more than 5, preferably notless than 1 and not more than 3, and more preferably not less than 1 andnot more than 2.

The Mw and Mn of the resin according to the present invention areamounts measured by using Gel Permeation Chromatography (GPC) with thecondition as described below.

GPC column: two G2000HXL, one G3000HXL, and one G4000HXL (allmanufactured from Tosoh Corporation)

Column temperature: 40° C.

Eluting solvent: tetrahydrofuran

Flow rate: 1.0 mL/min

Sample concentration: 1.0% by mass

Sample injection amount: 100 μL

Detector: Differential Refractometer

Reference material: monodisperse polystyrene

The content of the base resin is preferably not less than 70% by mass,more preferably not less than 80% by mass, and further preferably notless than 85% by mass based on the total solid content of theradiation-sensitive resin composition.

(Other Resin)

The radiation-sensitive resin composition of this embodiment may includea resin having higher content by mass of fluorine atoms than the baseresin as described above (hereinafter, also referred as a “highfluorine-containing resin”) as the other resin. When theradiation-sensitive resin composition includes the highfluorine-containing resin, the high fluorine-containing resin can belocalized on the surface layer of the resist film compared to the baseresin. Therefore, the water repellency of the surface of the resist filmcan be improved during the immersion exposure.

The high fluorine-containing resin is preferably one having a structureunit represented by the following formula (5) (hereinafter, alsoreferred as a “structure unit (IV)”) in addition to the structure unit(I) in the base resin as described above.

In the above formula (5), R¹³ is a hydrogen atom, a methyl group, or atrifluoromethyl group; G is a single bond, an oxygen atom, a sulfuratom, —COO—, —SO₂ONH—, —CONH—, or —OCONH—; R¹⁴ is a monovalentfluorinated chain hydrocarbon group having a carbon number of 1 to 20,or a monovalent fluorinated alicyclic hydrocarbon group having a carbonnumber of 3 to 20.

As R¹³ as described above, in terms of the copolymerizability ofmonomers resulting in the structure unit (IV), a hydrogen atom or amethyl group is preferred, and a methyl group is more preferred.

As G^(L) as described above, in terms of the copolymerizabilityofmonomers resulting in the structure unit (IV), a single bond or —COO— ispreferred, and —COO— is more preferred.

Example of the monovalent fluorinated chain hydrocarbon group having acarbon number of 1 to 20 represented by R¹⁴ as described above includesa group in which a part of or all of hydrogen atoms in the straight orbranched chain alkyl group having a carbon number of 1 to 20 is/aresubstituted with a fluorine atom.

Example of the monovalent fluorinated alicyclic hydrocarbon group havinga carbon number of 3 to 20 represented by R¹⁴ as described aboveincludes a group in which a part of or all of hydrogen atoms in themonocyclic or polycyclic hydrocarbon group having a carbon number of 3to 20 is/are substituted with a fluorine atom.

The R¹⁴ as described above is preferably a fluorinated chain hydrocarbongroup, more preferably a fluorinated alkyl group, and further preferably2,2,2-trifluoroethyl group, 1,1,1,3,3,3-hexafluoropropyl group and5,5,5-trifluoro-1,1-diethylpentyl group.

When the high fluorine-containing resin has the structure unit (IV), thelower limit of the content by percent of the structure unit (IV) ispreferably 10 mol %, more preferably 15 mol %, further preferably 20 mol%, and particularly preferably 25 mol % based on the total structureunits as the component of the high fluorine-containing resin. The upperlimit of the content by percent is preferably 60 mol %, more preferably50 mol %, and further preferably 40 mol %. By adjusting the content bypercent of the structure unit (IV) within the ranges, the content bymass percent of fluorine atoms of the high fluorine-containing resin canbe suitably adjusted to promote the localization of the highfluorine-containing resin on the surface layer of the resist film.Therefore, the water repellency of the surface of the resist film can beimproved during the immersion exposure.

The high fluorine-containing resin may include a structure unit having afluorine atom represented by the following formula (f-2) (hereinafter,also referred as a “structure unit (V)”) in addition to the structureunit (IV). The solubility of the high fluorine-containing resin into analkaline developing solution can be improved by including the structureunit (f-2), and thereby prevent from generating the development defect.

The structure unit (V) is classified into two groups: a unit having analkali soluble group (x); and a unit having a group (y) in which thesolubility into the alkaline developing solution is increased by thedissociation by alkali (hereinafter, simply referred as an“alkali-dissociable group”). In both cases of (x) and (y), R^(C) in theabove formula (f-2) is a hydrogen atom, a fluorine atom, a methyl group,or a trifluoromethyl group; R^(D) is a single bond, a hydrocarbon grouphaving a carbon number of 1 to 20 with the valency of (s+1), a structurein which an oxygen atom, a sulfur atom, —NR^(dd)—, a carbonyl group,—COO— or —CONH— is connected to the terminal on R^(E) side of thehydrocarbon group, or a structure in which a part of hydrogen atoms inthe hydrocarbon group is substituted with an organic group having ahetero atom; R^(dd) is a hydrogen atom, or a monovalent hydrocarbongroup having a carbon number of 1 to 10; and s is an integer of 1 to 3.

When the structure unit (V) has the alkali soluble group (x), R^(F) is ahydrogen atom; A¹ is an oxygen atom, —COO—* or —SO₂O—*; * refers to abond to R^(F); W¹ is a single bond, a hydrocarbon group having a carbonnumber of 1 to 20, or a divalent fluorinated hydrocarbon group. When A¹is an oxygen atom, W¹ is a fluorinated hydrocarbon group having afluorine atom or a fluoroalkyl group on the carbon atom connecting toA¹. R^(E) is a single bond, or a divalent organic group having a carbonnumber of 1 to 20. When s is 2 or 3, a plurality of R^(E), W¹, A¹ andR^(F) may be each identical or different. The affinity of the highfluorine-containing resin into the alkaline developing solution can beimproved by including the structure unit (V) having the alkali solublegroup (x), and thereby prevent from generating the development defect.As the structure unit (V) having the alkali soluble group (x),particularly preferred is a structure unit in which A¹ is an oxygen atomand W¹ is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

When the structure unit (V) has the alkali-dissociable group (y), R^(F)is a monovalent organic group having carbon number of 1 to 30; A¹ is anoxygen atom, —NR^(aa)—, —COO—*, or —SO₂O—*; R^(aa) is a hydrogen atom,or a monovalent hydrocarbon group having a carbon number of 1 to 10; *refers to a bond to R^(F); W¹ is a single bond, or a divalentfluorinated hydrocarbon group having a carbon number of 1 to 20; R^(E)is a single bond, or a divalent organic group having a carbon number of1 to 20. When A¹ is —COO—* or —SO₂O—*, W¹ or R^(F) has a fluorine atomon the carbon atom connecting to A¹ or on the carbon atom adjacent tothe carbon atom. When A¹ is an oxygen atom, W¹ and R^(E) are a singlebond; R^(D) is a structure in which a carbonyl group is connected at theterminal on R^(E) side of the hydrocarbon group having a carbon numberof 1 to 20; and R^(F) is an organic group having a fluorine atom. When sis 2 or 3, a plurality of R^(E), W¹, A¹ and R^(F) may be each identicalor different. The surface of the resist film is changed from hydrophobicto hydrophilic in the alkaline developing step by including thestructure unit (V) having the alkali-dissociable group (y). As a result,the affinity of the high fluorine-containing resin into the alkalinedeveloping solution can be significantly improved, and thereby preventfrom generating the development defect more efficiently. As thestructure unit (V) having the alkali-dissociable group (y), particularlypreferred is a structure unit in which A¹ is —COO—*, and R^(F) or W¹, orboth is/are a fluorine atom.

In terms of the copolymerizability of monomers resulting in thestructure unit (V), R^(C) is preferably a hydrogen atom or a methylgroup, and more preferably a methyl group.

When R^(E) is a divalent organic group, R^(E) is preferably a grouphaving a lactone structure, more preferably a group having a polycycliclactone structure, and further preferably a group having a norbornanelactone structure.

When the high fluorine-containing resin has the structure unit (V), thelower limit of the content by percent of the structure unit (V) ispreferably 10 mol %, more preferably 20 mol %, further preferably 30 mol%, and particularly preferably 35 mol % based on the total structureunits as the component of the high fluorine-containing resin. The upperlimit of the content by percent is preferably 90 mol %, more preferably75 mol %, and further preferably 60 mol %. By adjusting the content bypercent of the structure unit (V) within the ranges, the waterrepellency of the surface of the resist film can be further improvedduring the immersion exposure.

The lower limit of Mw of the high fluorine-containing resin ispreferably 1,000, more preferably 2,000, further preferably 3,000, andparticularly preferably 5,000. The upper limit of Mw is preferably50,000, more preferably 30,000, further preferably 20,000, andparticularly preferably 15,000.

The lower limit of the Mw/Mn of the high fluorine-containing resin istypically 1, and more preferably 1.1. The upper limit of the Mw/Mn istypically 5, preferably 3, more preferably 2, and further preferably1.7.

The lower limit of the content of the high fluorine-containing resin ispreferably 0.1% by mass, more preferably 0.5% by mass, furtherpreferably 1% by mass, and even further preferably 1.5% by mass based onthe total solid content of the radiation-sensitive resin composition.The upper limit of the content is preferably 20% by mass, morepreferably 15% by mass, further preferably 10% by mass, and particularlypreferably 7% by mass.

The lower limit of the content of the high fluorine-containing resin ispreferably 0.1 part by mass, more preferably 0.5 part by mass, furtherpreferably 1 part by mass, and particularly preferably 1.5 part by massbased on 100 parts by mass of total base resins. The upper limit of thecontent is preferably 15 parts by mass, more preferably 10 parts bymass, further preferably 8 parts by mass, and particularly preferably 5parts by mass.

By adjusting the content of the high fluorine-containing resin withinthe ranges, the high fluorine-containing resin can be localized on thesurface layer of the resist film more efficiently. Therefore, the waterrepellency of the surface of the resist film can be improved during theimmersion exposure. The radiation-sensitive resin composition maycontain one type of the high fluorine-containing resin, or two or morehigh fluorine-containing resins in combination.

(Method for Synthesizing High Fluorine-Containing Resin)

The high fluorine-containing resin can be synthesized by the similarmethod for the base resin as described above.

(Radiation-Sensitive Acid Generator)

The radiation-sensitive acid generator includes at least two ofcompounds represented by the following formulae (1) to (3), providedthat the compound represented by the formula (1) and the compoundrepresented by the formula (3) within the scope of the compoundrepresented by the formula (2) are excluded.

In the formulae (1) to (3),

R¹, R² and R³ are each independently a group having a cyclic structure;

X¹¹, X¹², X²¹, X²², X³³ and X³² are each independently a hydrogen atom,a fluorine atom, or a fluorinated hydrocarbon group, provided that bothX¹¹ and X¹², both X²¹ and X²², and both X³¹ and X³² are not a hydrogenatom, respectively;

A¹¹, A¹², A²¹, A²², A³¹ and A³² are each independently a hydrogen atom,or a hydrocarbon group having a carbon number of 1 to 20;

m¹, m² and m³ are each independently an integer of 0 to 5;

n¹, n² and n³ are each independently an integer of 1 to 4;

G is a single bond, or a divalent linking group; and

Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ are each independently a monovalent onium cation.

The group having a cyclic structure is not particularly limited as longas the group has a cyclic structure. The cyclic structure may be analicyclic structure, an aromatic ring structure, or a heterocyclic ringstructure, and a monocyclic or polycyclic structure, and saturated orunsaturated. The cyclic structure may be formed only by a ringstructure, or may have a chain structure in part thereof. When thecyclic structure has a chain structure in part thereof, a hetero atomsuch as O or S may be included between a carbon-carbon bond in the chainstructure. The heterocyclic ring structure is not particularly limited.Examples of the heterocyclic ring structure include a lactone structure,a cyclic carbonate structure, a cyclic acetal structure, a cyclic etherstructure, a sultone structure, and a cyclic amine structure. The grouphaving a cyclic structure may have a combination of these cyclicstructures. Among them, the preferred cyclic structure is an alicyclicgroup as the alicyclic structure, including a heterocyclic ringstructure in which a carbon atom forimng the alicyclic group issubstituted with a hetero atom.

The alicyclic group is preferably a group having a alicyclic hydrocarbongroup having a carbon number of 3 to 20. Such an alicyclic hydrocarbongroup may be monocyclic or polycyclic. Preferred examples of thealicyclic hydrocarbon group include a monocyclic cycloalkyl group,including a cyclopentyl group, a cyclohexyl group, and a cyclooctylgroup; and a polycyclic cycloalkyl group, including a norbornyl group, anorbornen-yl group, a tricyclodecanyl group (for example, atricyclo[5.2.1.0(2,6)]decanyl group), a tetracyclodecanyl group, atetracyclododecanyl group, and an adamantyl group. The carbon forimngthe alicyclic group (i.e., a carbon contributing to the formation of thering) may be a carbonyl carbon. The carbon forimng the alicyclic groupmay also be substituted with a hetero atom.

When a part of the carbon forimng the alicyclic group is a carbonylcarbon, the specific examples of the group include an oxocycloalkylgroup having a carbon number of 6 to 10, including a 2-oxo-cyclopentylgroup, a 2-oxo-cyclohexyl group, a 2-oxo-cycloheptyl group, a2-oxo-methyl cyclohexyl group, a 2-oxo-norbornyl group, a 2-oxo-bornylgroup, and a 6-oxo-1-adamantyl group.

Examples of the heterocyclic ring structure in which the carbon forimngthe alicyclic group is substituted with a hetero atom include cyclicstructures located at the terminal side with respect to L² in the aboveformulae (T-1) to (T-3), and (T-5) to (T-10); and structures having acyclic acetal represented by the following formulae (S-1) to (S-2).

In the above formulae, R^(J11), R^(J12), R^(J21) and R^(J22) are eachindependently a alicyclic hydrocarbon group having a carbon number of 3to 20, or an aromatic a hydrocarbon group having a carbon number of 6 to12; or R^(J11) and R^(J12) are combined together to form a cyclicstructure having a carbon number of 4 to 20, or R^(J21) and R^(J22) arecombined together to form a cyclic structure having a carbon number of 4to 20; q is an integer of 1 to 4; X^(G) is an oxygen atom or a methylenegroup. Example of the alicyclic hydrocarbon group having a carbon numberof 3 to 20 includes the alicyclic hydrocarbon group represented by R¹ asdescribed above. Examples of the aromatic hydrocarbon group having acarbon number of 6 to 12 include a phenyl group and a naphthyl group.Examples of the cyclic structure having a carbon number of 4 to 20,which is obtained by combining R^(J11) and R^(J12), and the cyclicstructure having a carbon number of 4 to 20, which is obtained bycombining R^(J21) and R^(J22) include a monocyclic cycloalkanestructure, including a cyclobutane structure, a cyclopentane structure,and a cyclohexane structure; and a polycyclic cycloalkane structure,including a norbornane structure, an adamantane structure, atricyclodecane structure, and a tetracyclododecane structure; and afluorene structure.

Examples of the substituent group with which a hydrogen atom in thealicyclic group may be substituted include a halogen atom, including afluorine atom, chlorine atom, bromine atom, and iodine atom; a hydroxygroup; a carboxy group; a cyano group; a nitro group; a straight orbranched chain alkyl group having a carbon number of 1 to 8; amonocyclic or polycyclic cycloalkyl group having a carbon number of 3 to20; an aryl group, including a phenyl group, a 1-naphthyl group, and a1-anthracenyl group; an alkoxy group, including a methoxy group, anethoxy group, and a tert-butoxy group; an alkoxycarbonyl group,including a methoxycarbonyl group, a butoxycarbonyl group, and anadamantylmethyloxycarbonyl group; an alkoxycarbonyloxy group, includinga methoxycarbonyloxy group, a butoxycarbonyloxy group, and anadamantylmethyloxycarbonyloxy group; an acyl group, including an acetylgroup, a propionyl group, a benzoyl group, and an acryloyl group; and anacyloxy group, including an acetyloxy group, a propionyloxy group, abenzoyloxy group, and an acryloyloxy group.

Examples of the fluorinated hydrocarbon group represented by X¹¹, X¹²,X²¹, X²², X³¹ and X³² include a monovalent fluorinated chain hydrocarbongroup having a carbon number of 1 to 20; and a monovalent fluorinatedalicyclic hydrocarbon group having a carbon number of 3 to 20.

Examples of the monovalent fluorinated chain hydrocarbon group having acarbon number of 1 to 20 include:

a fluorinated alkyl group, including a trifluoromethyl group, a2,2,2-trifluoroethyl group, a pentafluoroethyl group, a2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group,a heptafluoro n-propyl group, a heptafluoro i-propyl group, a nonafluoron-butyl group, a nonafluoro i-butyl group, a nonafluoro t-butyl group, a2,2,3,3,4,4,5,5-octafluoro n-pentyl group, a tridecafluoro n-hexylgroup, and a 5,5,5-trifluoro-1,1-diethylpentyl group;

a fluorinated alkenyl group, including a trifluoroethenyl group and apentafluoropropenyl group; and a fluorinated alkynyl group, including afluoroethynylgroup and a trifluoropropynyl group.

Examples of the monovalent fluorinated alicyclic hydrocarbon grouphaving a carbon number of 3 to 20 include:

a fluorinated cycloalkyl group, including a fluorocyclopentyl group, adifluorocyclopentyl group, a nonafluorocyclopentyl group, afluorocyclohexyl group, a difluorocyclohexyl group, anundecafluorocyclohexylmethyl group, a fluoronorbornyl group, afluoroadamantyl group, a fluorobornyl group, a fluoroisoborynyl group, afluorotricyclodecyl group, and a fluorotetracyclodecyl group; and

a fluorinated cycloalkenyl group, including a fluorocyclopentenyl groupand a nonafluorocyclohexenyl group.

The fluorinated hydrocarbon group is preferably the monovalentfluorinated chain hydrocarbon group having a carbon number of 1 to 20 asdescribed above, and more preferably a monovalent fluorinated chainhydrocarbon group having a carbon number of 1 to 10. As the monovalentfluorinated chain hydrocarbon group having a carbon number of 1 to 10, agroup having a carbon number of 1 to 10 in the monovalent fluorinatedchain hydrocarbon group having a carbon number of 1 to 20 as describedabove can be suitably applied.

Examples of the hydrocarbon group having a carbon number of 1 to 20represented by A¹¹, A¹², A²¹, A²², A³¹ and A³² include a chainhydrocarbon group having a carbon number of 1 to 10, a monovalentalicyclic hydrocarbon group having a carbon number of 3 to 20, and amonovalent aromatic hydrocarbon group having a carbon number of 6 to 20.

Examples of the chain hydrocarbon group having a carbon number of 1 to10 include:

an alkyl group, including a methyl group, an ethyl group, a n-propylgroup, an i-propyl group, a n-butyl group, a 2-methylpropyl group, a1-methylpropyl group, and a t-butyl group;

an alkenyl group, including an ethenyl group, a propenyl group, and abutenyl group; and

an alkynyl group, including an ethynyl group, a propynyl group, and abutynyl group.

Examples of the alicyclic hydrocarbon group having a carbon number of 3to 20 include:

a monocyclic cycloalkyl group, including a cyclopropyl group, acyclobutyl group, a cyclopentyl group, and a cyclohexyl group;

a polycyclic cycloalkyl group, including a norbornyl group, an adamantylgroup, a tricyclodecyl group, and a tetracyclododecyl group;

a cycloalkenyl group, including a cyclopropenyl group, a cyclobutenylgroup, a cyclopentenyl group, and a cyclohexenyl group; and

a polycyclic cycloalkenyl group, including a norbornenyl group, atricyclodecenyl group, and a tetracyclododecenyl group.

Examples of the monovalent aromatic hydrocarbon group having a carbonnumber of 6 to 20 include an aryl group, including a phenyl group, atolyl group, a xylyl group, a naphthyl group, and an anthryl group; andan aralkyl group, including a benzyl group, a phenethyl group, and anaphthylmethyl group.

As A¹¹, A¹², A²¹, A²², A³¹ and A³² as described above, a hydrogen atom,or a chain hydrocarbon group having a carbon number of 1 to 10 ispreferred.

m¹, m² and m³ are each independently an integer of 0 to 5, preferably aninteger of 0 to 3, more preferably an integer of 0 to 2, andparticularly preferably 0 or 1.

n¹, n² and n³ are each independently an integer of 1 to 4, preferably aninteger of 1 to 3, and more preferably 1 or 2.

Examples of the divalent linking group represented by G as describedabove include an alkanediyl group, a cycloalkanediyl group, analkenediyl group, arenediyl group, *—OR^(LA)—, and *COOR^(LA)—. (*refers to a bond to the side of R¹.) A part of or all of hydrogen atomsin the group may be substituted with a halogen atom including a fluorineatom or chlorine atom, or a cyano group.

Examples of the alkanediyl group include a methanediyl group, anethanediyl group, a propanediyl group, a butanediyl group, a hexanediylgroup, and an octanediyl group. The alkanediyl group is preferably analkanediyl group having a carbon number of 1 to 8.

Preferred examples of the cycloalkanediyl group include acycloalkanediyl group, including a cyclopentanediyl group, and acyclohexanediyl group; and a polycyclic cycloalkanediyl group, includinga norbornane diyl group and an adamantanediyl group. The cycloalkanediylgroup is preferably a cycloalkanediyl group having a carbon number of 5to 12.

Preferred examples of the alkenediyl group include an ethenediyl group,a propenediyl group, and a butenediyl group. The alkenediyl group ispreferably an alkenediyl group having a carbon number of 2 to 6.

Examples of the arenediyl group includes a phenylene group, a tolylenegroup, and a naphthylene group. The arenediyl group is preferably anarenediyl group having carbon number of 6 to 15.

Examples of R^(LA) include the alkanediyl group, the cycloalkanediylgroup, the alkenediyl group, and the arenediyl group as each describedabove.

Preferred examples of the divalent linking group represented by G asdescribed above include a single bond, a methanediyl group, anethanediyl group, —COOCH₂—, and *—COOCH₂CH₂—. (* refers to a bond to theside of R¹.)

Preferably, each of the molecular weight of an anionic moiety in theradiation-sensitive acid generator is 230 or more. The molecular weightis preferably not more than 600. By adjusting the molecular weightwithin the ranges, it is possible to control the diffusion length of anacid generated from the radiation-sensitive acid generator to thesuitable range, and provide various resist properties at higher level.

The monovalent onium cation represented by Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ asdescribed above is a cation degradable by irradiating with a radioactiveray. In the exposed part, a sulfonic acid is generated by reacting aproton generated by degradation of the radiation degradable onium cationwith the sulfonate anion as described above. Examples of the radioactiveray include ultraviolet ray, far ultraviolet ray, extreme ultravioletray (EUV); an electromagnetic wave including X ray and γ ray; anelectron beam; and a charged particle radiation such as α ray. Amongthem, far ultraviolet ray, EUV, or an electron beam is preferred. Thefar ultraviolet ray is preferably KrF excimer laser light (wavelength is248 nm) or ArF excimer laser light (wavelength is 193 nm), and morepreferably ArF excimer laser light.

Examples of the onium cation include a radiation degradable oniumcation, including S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi.Among them, a sulfonium cation having S (sulfur) as an element or aniodonium cation having I (iodine) as an element is preferred, andcations represented by the following formulae (X-1) to (X-5) are morepreferred.

In the above formula (X-1), R^(a1), R^(a2) and R^(a3) are eachindependently a substituted or unsubstituted, straight or branched chainalkyl group, alkoxy group or alkoxycarbonyloxy group having a carbonnumber of 1 to 12; a substituted or unsubstituted, monocyclic orpolycyclic cycloalkyl group having a carbon number of 3 to 12; asubstituted or unsubstituted aromatic hydrocarbon group having a carbonnumber of 6 to 12; a hydroxy group, —OSO₂—R^(P), —SO₂—R^(Q) or —S—R^(T);or a ring structure obtained by combining two or more of these groups.R^(P), R^(Q) and R^(T) are each independently a substituted orunsubstituted, straight or branched chain alkyl group having a carbonnumber of 1 to 12; a substituted or unsubstituted alicyclic hydrocarbongroup having a carbon number of 5 to 25; and a substituted orunsubstituted aromatic hydrocarbon group having a carbon number of 6 to12. k1, k2 and k3 are each independently an integer of 0 to 5. Whenthere are a plurality of R^(a1) to R^(a3) and a plurality of R^(P),R^(Q) and R^(T), a plurality of R^(a1) to R^(a3) and a plurality ofR^(P), R^(Q) and R^(T) may be each identical or different.

In the above formula (X-2), R^(b1) is a substituted or unsubstituted,straight chain or branched alkyl group or alkoxy group having a carbonnumber of 1 to 20; a substituted or unsubstituted acyl group having acarbon number of 2 to 8; or a substituted or unsubstituted aromatichydrocarbon group having a carbon number of 6 to 8; or a hydroxy group.n_(k) is 0 or 1. When n_(k) is 0, k4 is an integer of 0 to 4. When n_(k)is 1, k4 is an integer of 0 to 7. When there are a plurality of R^(b1),a plurality of R^(b1) may be each identical or different. A plurality ofR^(b1) may represent a ring structure obtained by combining them. R^(b2)is a substituted or unsubstituted, straight chain or branched alkylgroup having a carbon number of 1 to 7; or a substituted orunsubstituted aromatic hydrocarbon group having a carbon number of 6 to7. k5 is an integer of 0 to 4. When there are a plurality of R^(b2), aplurality of R^(b3) may be each identical or different. A plurality ofR^(b2) may represent a ring structure obtained by combining them. q isan integer of 0 to 3.

In the above formula (X-3), R^(c1), R^(C2) and R^(C3) are eachindependently a substituted or unsubstituted, straight or branched chainalkyl group having a carbon number of 1 to 12; or a substituted orunsubstituted aromatic hydrocarbon group having a carbon number of 6 to12.

In the above formula (X-4), R^(d1) and R^(d2) are each independently asubstituted or unsubstituted, straight or branched chain alkyl group,alkoxy group or alkoxycarbonyl group having a carbon number of 1 to 12;a substituted or unsubstituted aromatic hydrocarbon group having acarbon number of 6 to 12; a halogen atom; a halogenated alkyl grouphaving a carbon number of 1 to 4; a nitro group; or a ring structureobtained by combining two or more of these groups. k6 and k7 are eachindependently an integer of 0 to 5. When there are a plurality of R^(d1)and a plurality of R^(d2), a plurality of R^(d1) and a plurality ofR^(d2) may be each identical or different.

In the above formula (X-5), R^(e1) and R^(e2) are each independently ahalogen atom; a substituted or unsubstituted straight or branched chainalkyl group having a carbon number of 1 to 12; or a substituted orunsubstituted aromatic hydrocarbon group having a carbon number of 6 to12. k8 and k9 are each independently an integer of 0 to 4.

Examples of a substituent group with which an hydrogen atom in the groupas described above may be substituted include a halogen atom, includinga fluorine atom, a chlorine atom, a bromine atom, an iodine atom; ahydroxy group, a carboxy group, a cyano group, a nitro group, an alkylgroup (when a hydrogen atom in a cycloalkyl group or an aromatichydrocarbon group is substituted), an aryl group (when a hydrogen atomin an alkyl group is substituted), an alkoxy group, an alkoxycarbonylgroup, an alkoxycarbonyloxy group, an acyl group, and an acyloxy group.Among them, a hydroxy group, an alkoxy group, an alkoxycarbonyl group,an alkoxycarbonyloxy group, an acyl group, or an acyloxy group ispreferred. An alkoxy group or an alkoxycarbonyl group is more preferred.

Preferably, the compound represented by the above formula (1) is acompound represented by the following formula (1′), the compoundrepresented by the above formula (2) is a compound represented by thefollowing formula (2′), and the compound represented by the aboveformula (3) is a compound represented by the following formula (3′).

In the formulae (1′) to (3′),

R^(1a), R^(2a) and R^(3a) are each independently substituted orunsubstituted alicyclic group;

X¹, X¹², X²¹, X²², X³¹ and X³² are each independently a fluorine atom,or a monovalent fluorinated chain hydrocarbon group having a carbonnumber of 1 to 10;

A²¹, A²², A³¹ and A³² are each independently a hydrogen atom, or a chainhydrocarbon group having a carbon number of 1 to 10;

m^(2a) and m^(3a) are each independently 0 or 1;

n^(1a), n^(2a) and n^(3a) are each independently 1 or 2;

G has the same meaning as in the above formula (1); and

Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ each have the same meaning as in the above formulae(1) to (3).

As the alicyclic group, the monovalent fluorinated chain hydrocarbongroup having a carbon number of 1 to 10 and the chain hydrocarbon grouphaving a carbon number of 1 to 10, the alicyclic group, the monovalentfluorinated chain hydrocarbon group having a carbon number of 1 to 10and the chain hydrocarbon group having a carbon number of 1 to 10 in theabove formulae (1) to (3) may be suitably applied.

Examples of the compound represented by the above formula (1) includecompounds represented by the following formulae (1-1) to (1-10)(hereinafter, also referred as “compounds (1-1) to (1-10)”).

In the above formulae (1-1) to (1-10), Z is a monovalent onium cation.

Among them, compounds (1-1) to (1-5) are preferred as the compound (1).

Examples of the compound represented by the above formula (2) includecompounds represented by the following formulae (2-1) to (2-12)(hereinafter, also referred as “compounds (2-1) to (2-12)”).

In the above formulae (2-1) to (2-12), Z₂* is a monovalent onium cation.

Among them, compounds (2-1) to (2-6) are preferred as the compound (2).

Examples of the compound represented by the above formula (3) includecompounds represented by the following formulae (3-1) to (3-11)(hereinafter, also referred as “compounds (3-1) to (3-11)”).

In the above formulae (3-1) to (3-11), Z₃ ⁺ is a monovalent oniumcation.

Among them, compounds (3-1) to (3-2) are preferred as the compound (3).

Preferably, the radiation-sensitive acid generator is:

the compound represented by the above formula (1) and the compoundrepresented by the above formula (2);

the compound represented by the above formula (1) and the compoundrepresented by the above formula (3); or

the compound represented by the above formula (1), the compoundrepresented by the above formula (2) and the compound represented by theabove formula (3).

The various resist properties can be further improved by including atleast one of the compounds (2) and (3) as the radiation-sensitive acidgenerator in addition to the compound (1).

When at least one of the compounds (2) and (3) is included as theradiation-sensitive acid generator in addition to the compound (1), thecontent of the compound represented by the above formula (1) ispreferably not less than 1 part by mass and not more than 45 parts bymass based on 100 parts by mass of total resins. In this case, the lowerlimit of the content of the compound (1) is more preferably 2 parts bymass, and further preferably 3 parts by mass based on 100 parts by massof total resins. The upper limit of the content of the compound (1) ismore preferably 30 parts by mass, and further preferably 20 parts bymass based on 100 parts by mass of total resins. Thereby, the variousresist properties can be improved effectively.

In the radiation-sensitive resin composition of this embodiment, thelower limit of the total content of the radiation-sensitive acidgenerator is preferably 3 parts by mass, more preferably 5 parts bymass, and further preferably 7 parts by mass based on 100 parts by massof total base resins. The upper limit of the total content is preferably45 parts by mass, more preferably 37 parts by mass, and furtherpreferably 35 parts by mass. By adjusting the content of theradiation-sensitive acid generator within the ranges, a resist patternhaving improved various resist properties can be formed.

(Synthesis Method of Radiation-Sensitive Acid Generator)

The radiation-sensitive acid generator of this embodiment can beprepared by reacting the corresponding precursor compound (1α) with analkali metal salt of dithionous acid (for example, sodium salt) in thepresence of an inorganic base to form the sulfinic acid salt (2α),oxidizing the sulfinic acid salt with an oxidizing agent such ashydrogen peroxide to form the surfonic acid salt (3α) followed by theion-exchange reaction with a counter-ion exchange precursor Z⁺Y⁻.

In the above scheme, T is a monovalent leaving group; R is a groupcorresponding to a structure (including the precursor structure) fromthe carbon atom on which is substituted with A¹¹, A¹², A²¹, A²², A³¹ andA³² in the above formulae (1) to (3) to the ring structure at theterminal; X^(n1) or X^(n2) is a group corresponding to X¹¹, X¹², X²¹,X²², X³¹ and X³² in the above formulae (1) to (3); Z⁺ is a groupcorresponding to Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺; and Y⁻ is a monovalent anion.

(Solvent)

The radiation-sensitive resin composition includes a solvent. Thesolvent is not particularly limited as long as the solvent can dissolveor disperse at least the resin, the radiation-sensitive acid generator,and optionally an agent such as an acid diffusion controlling agent, ifneeded.

Examples of the solvent include an alcohol-based solvent, an ether-basedsolvent, a ketone-based solvent, an amide-based solvent, an ester-basedsolvent, and a hydrocarbon-based solvent.

Examples of the alcohol-based solvent include:

a monoalcohol-based solvent having a carbon number of 1 to 18, includingiso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol,2-ethylhexanol, furfuryl alcohol, cyclohexanol,3,3,5-trimethylcyclohexanol, and diacetone alcohol;

a polyhydric alcohol having a carbon number of 2 to 18, includingethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol,2,5-hexanediol, diethylene glycol, dipropylene glycol, triethyleneglycol, and tripropylene glycol; and

a partially etherized polyhydric alcohol-based solvent in which a partof hydroxy groups in the polyhydric alcohol-based solvent is etherized.

Examples of the ether-based solvent include:

a dialkyl ether-based solvent, including diethyl ether, dipropyl ether,and dibutyl ether;

a cyclic ether-based solvent, including tetrahydrofuran andtetrahydropyran;

an ether-based solvent having an aromatic ring, including diphenyletherand anisole (methyl phenyl ether); and

an etherized polyhydric alcohol-based solvent in which a hydroxy groupin the polyhydric alcohol-based solvent is etherized.

Examples of the ketone-based solvent include:

a chain ketone-based solvent, including acetone, butanone, andmethyl-iso-butyl ketone;

a cyclic ketone-based solvent, including cyclopentanone, cyclohexanone,and methylcyclohexanone; and

2,4-pentanedione, acetonylacetone, and acetophenone.

Examples of the amide-based solvent include:

a cyclic amide-based solvent, including N,N′-dimethyl imidazolidinoneand N-methylpyrrolidone; and

a chain amide-based solvent, including N-methylformamide,N,N-dimethylformamide, N,N-diethylformamide, acetamide,N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

Examples of the ester-based solvent include:

a monocarboxylate ester-based solvent, including n-butyl acetate andethyl lactate;

a partially etherized polyhydric alcohol acetate-based solvent,including diethylene glycol mono-n-butyl ether acetate, propylene glycolmonomethyl ether acetate, and dipropylene glycol monomethyl etheracetate;

a lactone-based solvent, including γ-butyrolactone and valerolactone;

a carbonate-based solvent, including diethyl carbonate, ethylenecarbonate, and propylene carbonate; and

a polyhydric carboxylic acid diester-based solvent, including propyleneglycol diacetate, methoxy triglycol acetate, diethyl oxalate, ethylacetoacetate, ethyl lactate, and diethyl phthalate.

Examples of the hydrocarbon-based solvent include:

an aliphatic hydrocarbon-based solvent, including n-hexane, cyclohexane,and methylcyclohexane;

an aromatic hydrocarbon-based solvent, including benzene, toluene,di-iso-propylbenzene, and n-amylnaphthalene.

Among them, the ester-based solvent or the ketone-based solvent ispreferred. The partially etherized polyhydric alcohol acetate-basedsolvent, the cyclic ketone-based solvent, or the lactone-based solventis more preferred. Propylene glycol monomethyl ether acetate,cyclohexanone, or γ-butyrolactone is still more preferred. Theradiation-sensitive resin composition may include one type of thesolvent, or two or more types of the solvents in combination.

(Other Optional Ingredient)

The radiation-sensitive resin composition may also include any otheroptional ingredient in addition to the ingredients as described above.Examples of the other optional ingredient include an acid diffusioncontrolling agent, a localization enhancing agent, a surfactant, analicyclic backbone-containing compound, and a sensitizer.

The other optional ingredient may be used alone, or two or more otheroptional ingredients may be used in combination.

(Acid Diffusion Controlling Agent)

The radiation-sensitive resin composition may include an acid diffusioncontrolling agent, if needed. The acid diffusion controlling agent hasan effect of controlling the diffusion phenomenon in which an acidresulted from the radiation-sensitive acid generator by the exposure isdiffused in the resist film, and of inhibiting undesired chemicalreaction in the non-exposed part. The acid diffusion controlling agentcan also improve the storage stability of the resultingradiation-sensitive resin composition. The acid diffusion controllingagent can further improve the resolution of the resist pattern andprevent from changing the line width of the resist pattern because ofthe variation of the pulling and placing time, i.e., the time from theexposure to the developing treatment, and therefore provide theradiation-sensitive resin composition having an improved processstability.

Examples of the acid diffusion controlling agent include a compoundrepresented by the following formula (7) (hereinafter, also referred asa “nitrogen-containing compound (I)”); a compound having two nitrogenatoms in one molecule (hereinafter, also referred as a“nitrogen-containing compound (II)”); a compound having three nitrogenatoms in one molecule (hereinafter, also referred as a“nitrogen-containing compound (III)”); a compound having an amide group;a urea compound; and a nitrogen-containing heterocyclic ring compound.

In the above formula (7), R²², R²³ and R²⁴ are each independently ahydrogen atom, a substituted or unsubstituted alkyl group, a substitutedor unsubstituted cycloalkyl group, a substituted or unsubstituted arylgroup, or a substituted or unsubstituted aralkyl group.

Examples of the nitrogen-containing compound (I) include amonoalkylamine including n-hexylamine; a dialkylamine includingdi-n-butylamine; a trialkylamine including triethylamine; and anaromatic amine including aniline.

Examples of the nitrogen-containing compound (II) includeethylenediamine and N,N,N′,N′-tetramethylethylenediamine.

Examples of the nitrogen-containing compound (III) include a polyaminecompound, including polyethyleneimine and polyallylamine; and a polymerincluding dimethylaminoethylacrylamide.

Examples of the amide-containing compound include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, andN-methyl pyrrolidone.

Examples of the urea compound include urea, methylurea,1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea,1,3-diphenylurea, and tributylthiourea.

Examples of the nitrogen-containing heterocyclic ring compound includepyridines, including pyridine and 2-methylpyridine; morpholines,including N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine;pyrazine, and pyrazole.

A compound having an acid-dissociable group may be used as thenitrogen-containing organic compound. Examples of thenitrogen-containing organic compound having an acid-dissociable groupinclude N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole,N-t-butoxycarbonylbenzimidazole,N-t-butoxycarbonyl-2-phenylbenzimidazole,N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine,N-(t-butoxycarbonyl)dicyclohexylamine,N-(t-butoxycarbonyl)diphenylamine,N-t-butoxycarbonyl-4-hydroxypiperidine, andN-t-amyloxycarbonyl-4-hydroxypiperidine.

A radiation-sensitive weak acid generator from which a weak acid isgenerated by the exposure may be suitably used as the acid diffusioncontrolling agent. An acid generated by the radiation-sensitive weakacid generator is a weak acid incapable of inducing dissociation of theacid-dissociable group in a condition that an acid generated by theradiation-sensitive acid generator dissociates the acid-dissociablegroup in the resin. As used herein, the “dissociation” of theacid-dissociable group means that the group is dissociated during thepost-exposure bake at 110° C. for 60 seconds.

Example of the radiation-sensitive weak acid generator includes an oniumsalt compound in which the compound is degraded by the exposure to losethe acid diffusion controlling properties. Examples of the onium saltcompound include a sulfonium salt compound represented by the followingformula (8-1), and an iodonium salt compound represented by thefollowing formula (8-2).

In the above formula (8-1) and formula (8-2), J⁺ is a sulfonium cation;and U⁺ is an iodonium cation. Examples of the sulfonium cationrepresented by J⁺ include sulfonium cations represented by the aboveformulae (X-1) to (X-3). Examples of the iodonium cation represented byU⁺ include iodonium cations represented by the above formulae (X-4) to(X-5). E⁻ and Q⁻ are each independently anion represented by OH⁻,R^(α)—COO⁻, and R^(α)—SO₃ ⁻. R^(α) is an alkyl group, an aryl group, oran aralkyl group. A hydrogen atom in the aromatic ring of the aryl groupor the aralkyl group represented by R^(α) may be substituted with ahydroxy group, a fluorine atom-substituted or unsubstituted alkyl grouphaving a carbon number of 1 to 12, or an alkoxy group having a carbonnumber of 1 to 12.

Examples of the radiation-sensitive weak acid generator includecompounds represented by the following formulae.

Among them, the radiation-sensitive weak acid generator is preferablythe sulfonium salt, more preferably a triarylsulfonium salt, and furtherpreferably a triphenylsulfonium salicylate or triphenylsulfonium10-camphorsulfonate.

The lower limit of the content of the acid diffusion controlling agentis preferably 3 parts by mass, more preferably 4 parts by mass, andfurther preferably 5 parts by mass based on 100 parts by mass of totalradiation-sensitive acid generators. The upper limit of the content ispreferably 150 parts by mass, more preferably 120 parts by mass, andfurther preferably 110 parts by mass.

By adjusting the content of the acid diffusion controlling agent withinthe ranges, the radiation-sensitive resin composition can provideimproved lithography properties. The radiation-sensitive resincomposition may contain one type of the acid diffusion controllingagent, or two or more acid diffusion controlling agents in combination.

(Localization Enhancing Agent)

The localization enhancing agent has an effect of localizing the highfluorine-containing resin on the surface of the resist film moreeffectively. The added amount of the high fluorine-containing resin canbe decreased compared to the traditionally added amount by including thelocalization enhancing agent in the radiation-sensitive resincomposition. The localization enhancing agent can further prevent fromeluting the ingredient of the composition from the resist film to animmersion medium and carry out the immersion exposure at higher speedwith a high-speed scan, while maintaining the lithography properties ofthe radiation-sensitive resin composition. As a result, thehydrophobicity of the surface of the resist film can be improved,resulting in the prevention of the defect due to the immersion, forexample, the watermark defect. Example of the compound which may be usedas the localization enhancing agent includes a low molecular weightcompound having a specific dielectric constant of not less than 30 andnot more than 200 and a boiling point of 100° C. or more at 1 atm.Specific examples of the compound include a lactone compound, acarbonate compound, a nitrile compound, and a polyhydric alcohol.

Examples of the lactone compound include γ-butyrolactone, valerolactone,mevaloniclactone, and norbornane lactone.

Examples of the carbonate compound include propylene carbonate, ethylenecarbonate, butylene carbonate, and vinylene carbonate.

Example of the nitrile compound includes succinonitrile.

Example of the polyhydric alcohol includes glycerine.

The lower limit of the content of the localization enhancing agent ispreferably 10 parts by mass, more preferably 15 parts by mass, furtherpreferably 20 parts by mass, and more further preferably 25 parts bymass based on 100 parts by mass of total resins in theradiation-sensitive resin composition. The upper limit of the content ispreferably 300 parts by mass, more preferably 200 parts by mass, furtherpreferably 100 parts by mass, and more further preferably 80 parts bymass. The radiation-sensitive resin composition may include one type ofthe localization enhancing agent, or two or more types of localizationenhancing agents in combination.

(Surfactant)

The surfactant has an effect of improving the coating properties, thestriation, and the developability of the composition. Examples of thesurfactant include a nonionic surfactant, including polyoxyethylenelauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleylether, polyoxyethylene n-octylphenyl ether, polyoxyethylenen-nonylphenyl ether, polyethylene glycol dilaurate, and polyethyleneglycol distearate. Examples of the surfactant which is commerciallyavailable include KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.),POLYFLOW No. 75, POLYFLOW No. 95 (all manufactured by Kyoeisha ChemicalCo., Ltd.), EFTOP EF301, EFTOP EF303, EFTOP EF352 (all manufactured byTokem Products), Megafac F171, Megafac F173 (all manufactured by DIC),Fluorad FC430, Fluorad FC431 (all manufactured by Sumitomo 3M Limited.),AsahiGuard AG710, Surflon S-382, Surflon SC-101, Surflon SC-102, SurflonSC-103, Surflon SC-104, Surflon SC-105, Surflon SC-106 (all manufacturedby Asahi Glass Co., Ltd.). The content of the surfactant in theradiation-sensitive resin composition is typically not more than 2 partsby mass based on 100 parts by mass of total resins.

(Alicyclic Backbone-Containing Compound)

The alicyclic backbone-containing compound has an effect of improvingthe dry etching resistance, the shape of the pattern, the adhesivenessbetween the substrate, and the like.

Examples of the alicyclic backbone-containing compound include:

adamantane derivatives, including 1-adamantane carboxylic acid,2-adamantanone, and t-butyl 1-adamantane carboxylate;

deoxycholic acid esters, including t-butyl deoxycholate,t-butoxycarbonylmethyl deoxycholate, and 2-ethoxyethyl deoxycholate;

lithocholic acid esters, including t-butyl lithocholate,t-butoxycarbonylmethyl lithocholate, and 2-ethoxyethyl lithocholate; and

3-[2-hydroxy-2,2-bis(trifluoromethyl)ethyl]tetra cyclo[4.4.0.12,5.17,10]dodecane, and2-hydroxy-9-methoxycarbonyl-5-oxo-4-oxa-tricyclo[4.2.1.03,7]nonane. Thecontent of the alicyclic backbone-containing compound in theradiation-sensitive resin composition is typically not more than 5 partsby mass based on 100 parts by mass of total resins.

(Sensitizer)

The sensitizer shows an action of increasing the production of the acid,for example, from the radiation-sensitive acid generator, and has aneffect of improving the “apparent sensitivity” of theradiation-sensitive resin composition.

Examples of the sensitizer include carbazoles, acetophenones,benzophenones, naphthalenes, phenols, biacetyl, eosin, rose bengal,pyrenes, anthracenes, and phenothiazines. The sensitizer may be usedalone, or two or more sensitizers may be used in combination. Thecontent of the sensitizer in the radiation-sensitive resin compositionis typically not more than 2 parts by mass based on 100 parts by mass oftotal resins.

<Method for Preparing Radiation-Sensitive Resin Composition>

For example, the radiation-sensitive resin composition can be preparedby mixing the resin, the radiation-sensitive acid generator, optionallythe acid diffusion controlling agent, the high fluorine-containingresin, and the solvent in a predetermined ratio. After mixing, theradiation-sensitive resin composition is preferably filtered, forexample, through a membrane filter having a pore size of about 0.05 μm.The solid concentration of the radiation-sensitive resin composition istypically from 0.1% by mass to 50% by mass, preferablly from 0.5% bymass to 30% by mass, and more preferably from 1% by mass to 20% by mass.

<Method for Forming Resist Pattern>

The method for forming a resist pattern includes the steps of:

forming a resist film from the radiation-sensitive resin composition(hereinafter, also referred as a “resist film forming step”);

exposing the resist film (hereinafter, also referred as a “exposingstep”); and

developing the exposed resist film (hereinafter, also referred as a“developing step”).

According to the method for forming a resist pattern, the resist patterncan be formed having an improved resolution, the rectangularity of thecross-section shape, LWR properties, depth of focus, MEEF properties,and the shrinkage control of the resist film during PEB. Each steps willbe described below.

[Resist Film Forming Step]

In this step, a resist film is formed from the radiation-sensitive resincomposition. Examples of the substrate on which the resist film isformed include one traditionally known in the art, including a siliconwafer, silicon dioxide, and a wafer coated with aluminum. An organic orinorganic antireflection film may be formed on the substrate, asdisclosed in JP-B-06-12452 and JP-A-59-93448. Examples of theapplicating method include a rotary coating (spin coating), flowcasting, and roll coating. After applicating, a prebake (PB) may becarried out in order to evaporate the solvent in the film, if needed.The temperature of PB is typically from 60° C. to 140° C., andpreferably from 80° C. to 120° C. The duration of PB is typically from 5seconds to 600 seconds, and preferably from 10 seconds to 300 seconds.The thickness of the resist film formed is preferably from 10 nm to1,000 nm, and more preferably from 10 nm to 500 nm.

When the immersion exposure is carried out, irrespective of presence ofa water repellent polymer additive such as the high fluorine-containingresin in the radiation-sensitive resin composition, the formed resistfilm may have a protective film for the immersion which is not solubleinto the immersion liquid on the film in order to prevent a directcontact between the immersion liquid and the resist film. As theprotective film for the immersion, a solvent-removable protective filmthat is removed with a solvent before the developing step (for example,see JP-A-2006-227632); or a developer-removable protective film that isremoved during the development of the developing step (for example, seeWO2005-069076 and WO2006-035790) may be used. In terms of thethroughput, the developer-removable protective film is preferably used.

When the subsequent exposing step is carried out by a radiation having awavelength of 50 nm or less, the resin having the structure units (I)and (III) as the base resin is preferably used in the composition.

[Exposing Step]

In this step, the resist film formed in the resist film forming step isexposed by irradiating with a radioactive ray through a photomask(optionally through an immersion medium such as water). Examples of theradioactive ray used for the exposure include visible ray, ultravioletray, far ultraviolet ray, extreme ultraviolet ray (EUV); anelectromagnetic wave including X ray and γ ray; an electron beam; and acharged particle radiation such as α ray. Among them, far ultravioletray, an electron beam, or EUV is preferred. ArF excimer laser light(wavelength is 193 nm), KrF excimer laser light (wavelength is 248 nm),an electron beam, or EUV is more preferred. An electron beam or EUVhaving a wavelength of 50 nm or less which is identified as the nextgeneration exposing technology is further preferred.

When the exposure is carried out by immersion exposure, examples of theimmersion liquid include water and fluorine-based inert liquid. Theimmersion liquid is preferably a liquid which is transparent withrespect to the exposing wavelength, and has a minimum temperature factorof the refractive index so that the distortion of the light imagereflected on the film becomes minimum. However, when the exposing lightsource is ArF excimer laser light (wavelength is 193 nm), water ispreferably used because of the ease of availability and ease of handlingin addition to the above considerations. When water is used, a smallproportion of an additive that decreases the surface tension of waterand increases the surface activity may be added. Preferably, theadditive can not dissolve the resist film on the wafer and can neglectan infuence on an optical coating at an under surface of a lens. Thewater used is preferably distilled water.

After the exposure, post exposure bake (PEB) is preferably carried outto promote the dissociation of the acid-dissociable group in the resinby the acid generated from the radiation-sensitive acid generator withthe exposure in the exposed part of the resist film. The difference ofsolubility into the developer between the exposed part and thenon-exposed part is generated by the PEB. The temperature of PEB istypically from 50° C. to 180° C., and preferably from 80° C. to 130° C.The duration of PEB is typically from 5 seconds to 600 seconds, andpreferably from 10 seconds to 300 seconds.

[Developing Step]

In this step, the resist film exposed in the exposing step is developed.By this step, the predetermined resist pattern can be formed. After thedevelopment, the resist pattern is washed with a rinse solution such aswater or alcohol, and the dried, in general.

Examples of the developer used for the development include, in thealkaline development, an alkaline aqueous solution obtained bydissolving at least one alkaline compound such as sodium hydroxide,potassium hydroxide, sodium carbonate, sodium silicate, sodiummetasilicate, ammonia water, ethylamine, n-propylamine, diethylamine,di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine,triethanolamine, tetramethyl ammonium hydroxide (TMAH), pyrrole,piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene,1,5-diazabicyclo-[4.3.0]-5-nonene. Among them, an aqueous TMAH solutionis preferred, and 2.38% by mass of aqueous TMAH solution is morepreferred.

In the case of the development with organic solvent, examples of thesolvent include an organic solvent, including a hydrocarbon-basedsolvent, an ether-based solvent, an ester-based solvent, a ketone-basedsolvent, and an alcohol-based solvent; and a solvent containing anorganic solvent. Examples of the organic solvent include one, two ormore solvents listed as the solvent for the radiation-sensitive resincomposition. Among them, an ester-based solvent or a ketone-basedsolvent is preferred. The ester-based solvent is preferably an acetateester-based solvent, and more preferably n-butyl acetate or amylacetate. The ketone-based solvent is preferably a chain ketone, and morepreferably 2-heptanone. The content of the organic solvent in thedeveloper is preferably not less than 80% by mass, more preferably notless than 90% by mass, further preferably not less than 95% by mass, andparticularly preferably not less than 99% by mass. Examples of theingredient other than the organic solvent in the developer include waterand silicone oil.

Examples of the developing method include a method of dipping thesubstrate in a tank filled with the developer for a given time (dipmethod); a method of developing by putting and leaving the developer onthe surface of the substrate with the surface tension for a given time(paddle method); a method of spraying the developer on the surface ofthe substrate (spray method); and a method of injecting the developerwhile scanning an injection nozzle for the developer at a constant rateon the substrate rolling at a constant rate (dynamic dispense method).

EXAMPLES

Although the present invention will be specifically described withreference to Examples, it is not intended that the present invention islimited to these Examples.

The measurement method for various properties will be described below.

[Measurement of Weight Average Molecular Weight (Mw), Number AverageMolecular Weight (Mn) and Dispersity (Mw/Mn)]

The Mw and Mn of the resin were measured by Gel PermeationChromatography (GPC) with GPC columns from Tosoh Corporation (twoG2000HXLs, one G3000HXL, and one G4000HXL) under the condition asdescribed below. The dispersity (Mw/Mn) was calculated by themeasurement results of Mw and Mn.

Eluting Solvent: tetrahydrofuran

Flow Rate: 1.0 mL/min

Sample Concentration: 1.0% by mass

Sample Injection Amount: 100 μL

Column Temperature: 40° C.

Detector: differential refractometer

Reference Material: monodisperse polystyrene

[¹H-NMR Analysis and ¹³C-NMR Analysis]

The content by percent (mol %) of each structure units in each resinswas analyzed by using “JNM-Delta400” manufactured by JEOL Ltd.

<Synthesis of Base Resin and High Fluorine-Containing Resin>

The compounds (M-1) to (M-5) as described below were used as monomerswhich were used for the synthesis of each resins in each Examples andeach Comparative Examples. It is noted that in the Synthesis Examples,parts by mass means an amount assuming that total mass of the usedmonomers is 100 parts by mass, and that mol % means an amount assumingthat total mole numbers of the used monomers is 100 mol %, unlessotherwise specified.

Synthesis Example 1

(Synthesis of Base Resin (A-1))

The compound (M-1), the compound (M-2) and the compound (M-3) asmonomers were dissolved in 2-butanone (200 parts by mass) at molar ratioof 40/10/50. AIBN (5 mol %) was added as an initiator to prepare amonomer solution. To a reactor was added 2-butanone (100 parts by mass),and the reactor was purged with nitrogen gas for 30 minutes. Thetemperature in the reactor was set at 80° C., and the monomer solutionwas added dropwise to the reactor under agitation for 3 hours. The startof the addition was regarded as the start time of the polymerizationreaction, and the polymerization reaction was continued for 6 hours.After completing the polymerization reaction, the polymer solution wascooled to 30° C. or less by cooling with water. The cooled polymersolution was poured to methanol (2,000 parts by mass). The precipitatedwhite powder was filtered. The filtered white powder was washed withmethanol twice, filtered, and dried at 50° C. for 17 hours to obtain abase resin (A-1) as white powder in good yield. The Mw of the base resin(A-1) was 7,800, and the Mw/Mn was 1.41. As a result of ¹³C-NMRanalysis, the content by percent of each structure unit derived from thecompounds (M-1), (M-2) and (M-3) was 40.2 mol %, 9.1 mol % and 50.7 mol%, respectively.

Synthesis Example 2

(Synthesis of Base Resin (A-2))

The compound (M-1), the compound (M-2) and the compound (M-4) asmonomers were dissolved in propylene glycol monomethyl ether (100 partsby mass) at molar ratio of 40/10/50. AIBN (6 mol %) as an initiator andt-dodecyl mercaptan (38 parts by mass per 100 parts by mass of theinitiator) as a chain transfer agent was added to prepare a monomersolution. The monomer solution was subjected to copolymerization undernitrogen atmosphere for 16 hours while maintaining the reactiontemperature at 70° C. After completing the polymerization reaction, thepolymer solution was added dropwise in n-hexane (1,000 parts by mass)and the polymer was solidified and purified. To the polymer was addedpropylene glycol monomethyl ether (150 parts by mass) additionally.Further, methanol (150 parts by mass), triethylamine (1.5 molarequivalent based on the used amount of the compound (M-4)) and water(1.5 molar equivalent based on the used amount of the compound (M-4))were added, and hydrolyzed for 8 hours while refluxing at the boilingpoint. After completing the reaction, the solvent and triethylamine wereevaporated under reduced pressure. The resulting polymer was dissolvedin acetone (150 parts by mass), and added dropwize in water (2,000 partsby mass) to solidify the polymer. The resulting white powder wasfiltered. The white powder was dried at 50° C. for 17 hours to obtain abase resin (A-2) as white powder in good yield. The Mw of the base resin(A-2) was 6,000, and the Mw/Mn was 1.81. As a result of ¹³C-NMRanalysis, the content by percent of each structure unit derived from thecompounds (M-1), (M-2) and (M-4) was 41.3 mol %, 8.0 mol % and 50.7 mol%, respectively.

Synthesis Example 3

(Synthesis of High Fluorine-Containing Resin (D-1))

The compound (M-1) and the compound (M-5) as monomers were dissolved in2-butanone (200 parts by mass) at molar ratio of 70/30. AIBN (5 mol %based on the total monomers) was added as an initiator to prepare amonomer solution. To a reactor was added 2-butanone (100 parts by mass),and the reactor was purged with nitrogen gas for 30 minutes. Thetemperature in the reactor was set at 80° C., the monomer solution wasadded dropwise to the reactor under agitation for 3 hours. The start ofthe addition was regarded as the start time of the polymerizationreaction, and the polymerization reaction was continued for 6 hours.After completing the polymerization reaction, the polymer solution wascooled to 30° C. or less by cooling with water. The solvent was replacedwith acetonitrile (400 parts by mass). Hexane (100 parts by mass) wasadded and stirred, and the acetonitrile layer was collected. Thecollection was repeated three times in total. By replacing the solventwith propylene glycol monomethyl ether acetate, a solution of the highfluorine-containing resin (D-1) was obtained in good yield. The Mw ofthe polymer (D-1) was 7,300, and the Mw/Mn was 2.00. As a result of¹³C-NMR analysis, the content by percent of each structure unit derivedfrom the compounds (M-1) and (M-5) was 71.1 mol % and 28.9 mol %,respectively.

The content by percent, the Mw and the Mw/Mn of each structure units inthe resulting resin are shown in Table 1. It is noted that “-” in thefollowing table means that the corresponding ingredient is not used.

TABLE 1 Monomer 1 Monomer 2 Monomer 3 Used Used Used amount amountamount Resin Type (mol %) Type (mol %) Type (mol %) Mw Mw/Mn SynthesisA-1 M-1 40 M-2 10 M-3 50 7,800 1.41 Example 1 Synthesis A-2 M-1 40 M-210 M-4* 50 6,000 1.81 Example 2 Synthesis D-1 M-1 70 — — M-5 30 7,3002.00 Example 3 *In the base resin (A-2), it is presented asp-hydroxystyrene structure unit derived from the compound (M-4).

<Preparation of Radiation-Sensitive Resin Composition>

Ingredients other than the base resin and the high fluorine-containingresin will now be described as the components of the radiation-sensitiveresin composition.

(Radiation-Sensitive Acid Generator)

The compounds represented by the following formulae (1-1) to (1-5),(2-1) to (2-6) and (3-1) to (3-2) (hereinafter, also referred as a“compound (1-1)” and the like) were used as the radiation-sensitive acidgenerator.

(Acid Diffusion Controlling Agent)

The compounds represented by the following formulae (C-1) to (C-3)(hereinafter, also referred as a “compound (C-1)” and the like) wereused as the acid diffusion controlling agent.

(Solvent)

The following (E-1) to (E-4) were used as the solvent.

E-1: propylene glycol monomethyl ether acetate

E-2: cyclohexanone

E-3: γ-butyrolactone

E-4: ethyl lactate

Example 1

The radiation-sensitive resin composition (J-1) was prepared by mixing100 parts by mass of the base resin (A-1), 5 parts by mass of thecompound (1-1) and 5 parts by mass of the compound (2-1) as theradiation-sensitive acid generator, 7 parts by mass of the compound(C-1) as the acid diffusion controlling agent, 3 parts by mass of thehigh fluorine-containing resin (D-1), and 2,240 parts by mass of (E-1),960 parts by mass of (E-2) and 30 parts by mass of (E-3) as the solvent,and then filtering through a membrane filter having a pore size of 0.2μm.

Examples 2-20 and Comparative Examples 1-7

The radiation-sensitive resin compositions (J-2) to (J-20) and (K-1) to(K-7) were prepared by using the method similar as in Example 1, exceptthat the type and content of each ingredients as shown in Table 2 wereused.

TABLE 2 Acid High Radiation- diffusion fluorine- sensitive acidcontrolling containing Base resin generator agent resin SolventRadiation- Content Content Content Content Content Content sensitive(Parts (Parts (Parts (Parts (Parts (Parts resin by by by by by bycomposition Type mass) Type mass) Type mass) Type mass) Type mass) Typemass) Example 1 J-1 A-1 100 1-1 5 2-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 2 J-2 A-1 100 1-1 5 2-2 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 3 J-3 A-1 100 1-1 5 2-3 5 C-2 7 D-1 3 E-1/E-2/E-32240/960/30 Example 4 J-4 A-1 100 1-1 5 2-4 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 5 J-5 A-1 100 1-1 5 2-5 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 6 J-6 A-1 100 1-1 5 2-6 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 7 J-7 A-1 100 1-1 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 8 J-8 A-1 100 1-1 5 3-2 5 C-3 4 D-1 3 E-1/E-2/E-32240/960/30 Example 9 J-9 A-1 100 1-1 5 2-1 5 C-3 4 D-1 3 E-1/E-2/E-32240/960/30 Example 10 J-10 A-1 100 1-2 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 11 J-11 A-1 100 1-2 5 2-1 5 C-2 7 D-1 3 E-1/E-2/E-32240/960/30 Example 12 J-12 A-1 100 1-3 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 13 J-13 A-1 100 1-4 5 2-1 5 C-3 4 D-1 3 E-1/E-2/E-32240/960/30 Example 14 J-14 A-1 100 2-1 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 15 J-15 A-1 100 2-2 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 16 J-16 A-1 100 2-3 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 17 J-17 A-1 100 2-4 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 18 J-18 A-1 100 2-5 5 3-1 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 19 J-19 A-1 100 2-6 5 3-2 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 Example 20 J-20 A-1 100 2-1 5 3-1 5 C-3 4 D-1 3 E-1/E-2/E-32240/960/30 Comparative K-1 A-1 100 1-1 5 1-2 5 C-1 7 D-1 3 E-1/E-2/E-32240/960/30 example 1 Comparative K-2 A-1 100 2-1 5 2-6 5 C-1 7 D-1 3E-1/E-2/E-3 2240/960/30 example 2 Comparative K-3 A-1 100 3-1 5 3-2 5C-1 7 D-1 3 E-1/E-2/E-3 2240/960/30 example 3 Comparative K-4 A-1 1001-1 10 — — C-2 7 D-1 3 E-1/E-2/E-3 2240/960/30 example 4 Comparative K-5A-1 100 1-5 10 — — C-1 7 D-1 3 E-1/E-2/E-3 2240/960/30 example 5Comparative K-6 A-1 100 2-6 10 — — C-1 7 D-1 3 E-1/E-2/E-3 2240/960/30example 6 Comparative K-7 A-1 100 3-1 10 — — C-1 7 D-1 3 E-1/E-2/E-32240/960/30 example 7

<Formation of Resist Pattern (1): Immersion Exposure by ArF ExcimerLaser, Development with Organic Solvent>

To a surface of a 12 inch silicon wafer was applied an underlayerantireflection film forming composition (“ARC66” manufactured by BrewerScience Incorporated.) by using a spin coater (“CLEAN TRACK ACT12”manufactured by Tokyo Electron Limited.). After applying, the wafer washeated at 205° C. for 60 seconds to form an underlayer antireflectionfilm having a film thickness of 105 nm. Each radiation-sensitive resincomposition was applied on the underlayer antireflection film by usingthe spin coater. The PAB (Post applied baking; baking after applying)was carried out at 100° C. for 50 seconds, and then cooled at 23° C. for30 seconds to form a resist film having a film thickness of 90 nm. Next,the resist film was exposed through a mask pattern for forming a resistpattern having a hole of 58 nm and a pitch of 96 nm with an ArF excimerlaser immersion exposure apparatus (“TWINSCAN XT-1900i” manufactured byASML) in a optical condition of NA=1.35 and Annular (σ=0.8/0.6). Afterexposing, the PEB was carried out at 90° C. for 50 seconds. The resistfilm was subjected to a paddle development by using n-butyl acetate at23° C. for 10 seconds. The resist film was spin dried at 2,000 rpm for15 seconds with spinning off to form a resist pattern having a hole of48 nm and a pitch of 96 nm. The exposed amount in which the size of thehole pattern was 48 nm during the formation of the resist pattern wasregarded as optimum exposed amount (Eop).

<Formation of Resist Pattern (2): Immersion Exposure by ArF ExcimerLaser, Alkaline Development>

To a surface of a 12 inch silicon wafer was applied an underlayerantireflection film forming composition (“ARC66” manufactured by BrewerScience Incorporated.) by using a spin coater (“CLEAN TRACK ACT12”manufactured by Tokyo Electron Limited.). After applying, the wafer washeated at 205° C. for 60 seconds to form an underlayer antireflectionfilm having a film thickness of 105 nm. Each radiation-sensitive resincomposition was applied on the underlayer antireflection film by usingthe spin coater. The PAB was carried out at 100° C. for 50 seconds, andthen cooled at 23-C for 30 seconds to form a resist film having a filmthickness of 90 nm. Next, the resist film was exposed through a maskpattern for forming a resist pattern having 38 nm line and space (1L/1S)with an ArF excimer laser immersion exposure apparatus (“TWINSCANXT-1900i” manufactured by ASML) in a optical condition of NA=1.35 andDipole35X (σ=0.97/0.77). After exposing, the PEB was carried out at 90°C. for 50 seconds. The resist film was subjected to a paddle developmentby using 2.38% by mass of aqueous TMAH solution at 23° C. for 30seconds, and rinsed with ultrapure water for 7 seconds. The resist filmwas spin dried at 2,000 rpm for 15 seconds with spinning off to form aresist pattern having 40 nm line and space (1L/1S). During the formationof the resist pattern, the exposed amount in which the line was formedthrough a mask pattern for forming a pattern having 40 nm line and space(1L/1S) as the target size, and the width of the formed line was 40 nmwas regarded as optimum exposed amount (Eop).

<Evaluation>

Using the formed resist patterns, each radiation-sensitive resincomposition was evaluated by measuring according to the followingmethod. The evaluation results are shown in the following Table 3. Thescanning electron microscope (“CG-5000” manufactured by HitachiHigh-Technologies Corporation) was used for measuring the length of theresist pattern.

[CDU Properties]

The hole pattern formed by exposing to the exposed amount as same as theEop calculated in the Formation of Resist Pattern (1) was observed fromthe top of the pattern by using the scanning electron microscope. Thehole diameter was measured at 16 points within a square 400 nm on aside, and the measurement values were averaged to determine the averagevalue. The average value was measured at five hundred of arbitrarypoints. The 3σ value was calculated from the distribution of themeasurement values, and the 3σ value was regarded as CDU properties(nm). The smaller the value is, the smaller the variation of the holediameter over long period is, which is better. As the CDU properties, ifthe value was not more than 5.0 nm, it was evaluated as “good”. If thevalue exceeded 5.0 nm, it was evaluated as “poor”.

[MEEF Properties]

The hole pattern formed by exposing to the exposed amount as same as theEop calculated in the Formation of Resist Pattern (1) was observed fromthe top of the pattern by using the scanning electron microscope. Thehole diameter was measured at 16 points within a square 400 nm on aside, and the measurement values were averaged to determine the averagevalue. The average value was measured at one hundred of arbitrarypoints. Similar measurement was each carried out in five conditions thatthe size of the mask was different by 1 nm. The amount of change in thehole diameter with respect to the amount of change in the mask wasregarded as MEEF properties (nm). The smaller the value of the MEEFproperties is, the better the mask fidelity is, which is better. As theMEEF properties, if the value was not more than 3.9 nm, it was evaluatedas “good”. If the value exceeded 3.9 nm, it was evaluated as “poor”.

[LWR Properties]

The line and space pattern formed by exposing to the exposed amount assame as the Eop calculated in the Formation of Resist Pattern (2) wasobserved from the top of the pattern by using the scanning electronmicroscope. The variation of the line width was measuredat at fivehundred points. The 3a value was calculated from the measurement values,and the 3a value was regarded as LWR properties (nm). The smaller thevalue of the LWR properties is, the smaller the wobble of the line is,which is better. As the LWR properties, if the value was not more than3.9 nm, it was evaluated as “good”. If the value exceeded 3.9 nm, it wasevaluated as “poor”.

TABLE 3 Development with Alkaline organic solvent developmentRadiation-sensitive CDU MEEF LWR resin composition (nm) (nm) (nm)Example 1 J-1 4.0 3.2 2.9 Example 2 J-2 4.1 3.2 2.9 Example 3 J-3 4.03.1 2.8 Example 4 J-4 4.1 3.2 2.9 Example 5 J-5 4.3 3.3 3.0 Example 6J-6 4.2 3.4 3.0 Example 7 J-7 4.4 3.4 3.2 Example 8 J-8 4.7 3.7 3.8Example 9 J-9 4.7 3.7 3.8 Example 10 J-10 4.5 3.5 3.3 Example 11 J-114.2 3.2 3.0 Example 12 J-12 4.2 3.3 3.1 Example 13 J-13 4.3 3.4 3.5Example 14 J-14 4.3 3.6 3.6 Example 15 J-15 4.1 3.6 3.5 Example 16 J-164.4 3.7 3.6 Example 17 J-17 4.5 3.5 3.4 Example 18 J-18 4.4 3.5 3.2Example 19 J-19 4.5 3.6 3.5 Example 20 J-20 4.7 3.7 3.8 Comparative K-16.0 4.7 4.6 example 1 Comparative K-2 6.1 4.7 4.4 example 2 ComparativeK-3 6.0 4.7 4.5 example 3 Comparative K-4 6.1 4.6 4.5 example 4Comparative K-5 6.2 4.7 4.3 example 5 Comparative K-6 6.3 4.3 4.6example 6 Comparative K-7 6.4 4.4 4.5 example 7

Example 21

The radiation-sensitive resin composition (J-21) was prepared by mixing100 parts by mass of the base resin (A-2), 17 parts by mass of thecompound (1-1) and 17 parts by mass of the compound (2-1) as theradiation-sensitive acid generator, 2.5 parts by mass of the compound(C-2) as the acid diffusion controlling agent, and 4,280 parts by massof (E-1) and 1,830 parts by mass of (E-4) as the solvent, and thenfiltering through a membrane filter having a pore size of 0.2 m.

Examples 22-23 and Comparative Examples 8-10

The radiation-sensitive resin compositions (J-22) to (J-23) and (K-8) to(K-10) were prepared by using the method similar as in Example 21,except that the type and content of each ingredients as shown in Table 4were used.

TABLE 4 Acid diffusion Radiation-sensitive controlling Radiation- Baseresin acid generator agent Solvent sensitive Content Content ContentContent Content resin (Parts by (Parts by (Parts by (Parts by (Partscomposition Type mass) Type mass) Type mass) Type mass) Type by mass)Example 21 J-21 A-2 100 1-1 17 2-1 17 C-2 2.5 E-1/E-4 4280/1830 Example22 J-22 A-2 100 1-1 17 2-2 17 C-2 2.5 E-1/E-4 4280/1830 Example 23 J-23A-2 100 1-1 17 2-3 17 C-2 2.5 E-1/E-4 4280/1830 Comparative K-8 A-2 1001-1 5 1-2 5 C-3 2.5 E-1/E-4 4280/1830 example 8 Comparative K-9 A-2 1002-1 5 2-6 5 C-2 2.5 E-1/E-4 4280/1830 example 9 Comparative K-10 A-2 1003-1 5 3-2 5 C-2 2.5 E-1/E-4 4280/1830 example 10

<Formation of Resist Pattern (3): Exposure with Electron Beam, AlkalineDevelopment>

To a surface of a 8 inch silicon wafer was applied eachradiation-sensitive resin composition as described in the above Table 4by using a spin coater (“CLEAN TRACK ACT8” manufactured by TokyoElectron Limited.). The PB was carried out at 90° C. for 60 seconds, andthen cooled at 23° C. for 30 seconds to form a resist film having a filmthickness of 50 nm. The resist film was exposed to an electron beam witha simplified model of Electron Beam Lithography Apparatus (manufacturedby Hitachi, Ltd., model “HL800D”, power output: 50 KeV, current density:5.0 A/cm²). After exposing, the PEB was carried out at 120° C. for 60seconds. The resist film was developed by using 2.38% by mass of aqueousTMAH solution as the alkaline developing solution at 23° C. for 30seconds, washed with water, and then dried to form a positive resistpattern having a hole of 100 nm and a pitch of 200 nm.

<Evaluation>

Using the formed resist patterns, the CDU properties of eachradiation-sensitive resin composition was evaluated by exposing to theoptimum exposed amount (Eop) according to the method as described above.The scanning electron microscope (S-9380 manufactured by HitachiHigh-Technologies Corporation) was used for measuring the length of theresist pattern. The results are shown in the following Table 5.

TABLE 5 Alkaline development Radiation-sensitive Eop CDU resincomposition (mJ) (nm) Example 21 J-21 33.0 2.9 Example 22 J-22 31.0 3.0Example 23 J-23 32.0 3.1 Comparative K-8 40.0 4.6 example 8 ComparativeK-9 33.0 4.7 example 9 Comparative K-10 35.0 4.8 example 10

As shown in Table 3 and Table 5, the radiation-sensitive resincompositions of Examples had good CDU properties, MEEF properties andLWR properties when the exposure with ArF was carried out. When theexposure with an electron beam was carried out, the compositions hadgood CDU properties. Therefore, the radiation-sensitive resincompositions are judged to have superior CDU properties, MEEF propertiesand LWR properties. In contrast, in the radiation-sensitive resincompositions of Comparative Examples, at least a part of theseproperties was poor. In general, it is known that in the exposure withan electron beam, the compositions show trends similar as in the EUVexposure. Therefore, it is expected that the radiation-sensitive resincompositions of Examples also has good CDU properties in EUV exposure.

INDUSTRIAL APPLICABILITY

According to the radiation-sensitive resin composition and the methodfor forming a resist pattern of the invention, the desired resistpattern can be formed having superior CDU properties, MEEF propertiesand LWR properties. Therefore, the composition and the method can besuitably used for producing a semiconductor device which is expected tobe further micronized in the future.

What is claimed is:
 1. A radiation-sensitive resin composition,comprising: a base resin comprising a structure unit having anacid-dissociable group, a content of the structural unit in the baseresin being 30-75 mol %; a radiation-sensitive acid generator; an aciddiffusion controlling agent; a fluorine-containing resin having a highercontent by mass of fluorine atoms than the base resin; and a solventwhich is at least one solvent selected from the group consisting ofiso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol,2-ethylhexanol, furfuryl alcohol, cyclohexanol,3,3,5-trimethylcyclohexanol, ethylene glycol, 1,2-propylene glycol,2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropyleneglycol, triethylene glycol, tripropylene glycol, a partially etherizedpolyhydric alcohol-based solvent in which a part of hydroxy groups inthe polyhydric alcohol is etherized, an ether-based solvent, acetone,butanone, methyl-iso-butyl ketone, cyclopentanone, cyclohexanone,methylcyclohexanone, 2,4-pentanedione, acetonylacetone, acetophenone, anamide-based solvent, an ester-based solvent, and a hydrocarbon-basedsolvent, wherein the radiation-sensitive acid generator comprises: asecond compound which is at least one compound selected from the groupconsisting of a compound represented by formula (2-1), a compoundrepresented by formula (2-2), a compound represented by formula (2-3), acompound represented by formula (2-4), a compound represented by formula(2-5), a compound represented by formula (2-6), a compound representedby formula (2-7), a compound represented by formula (2-8), a compoundrepresented by formula (2-9), a compound represented by formula (2-10),a compound represented by formula (2-11), and a compound represented byformula (2-12); a third compound which is at least one compound selectedfrom the group consisting of a compound represented by formula (3-1), acompound represented by formula (3-2), a compound represented by formula(3-3), a compound represented by formula (3-4), a compound representedby formula (3-5), a compound represented by formula (3-6), a compoundrepresented by formula (3-7), a compound represented by formula (3-8), acompound represented by formula (3-9), a compound represented by formula(3-10), and a compound represented by formula (3-11); and optionally, afirst compound represented by formula (1):

wherein: R¹ is a group having a cyclic structure; X¹¹ and X¹² are eachindependently a hydrogen atom, a fluorine atom, or a fluorinatedhydrocarbon group, provided that at least one of X¹¹ and X¹² is not ahydrogen atom; A¹¹ and A¹² are each independently a hydrogen atom, or ahydrocarbon group having a carbon number of 1 to 20; m¹ is an integer of0 to 5; n¹ is an integer of 1 to 4; G is a single bond, or a divalentlinking group; and Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ are each independently amonovalent onium cation, wherein an amount of the radiation-sensitiveacid generator is from 7 to 35 mass parts with respect to 100 mass partsof the base resin, an amount of the acid diffusion controlling agent isfrom 5 to 110 mass parts with respect to 100 mass parts of theradiation-sensitive acid generator, and an amount of thefluorine-containing resin is from 1 to 5 mass parts with respect to 100mass parts of the base resin.
 2. The radiation-sensitive resincomposition according to claim 1, wherein the radiation-sensitive acidgenerator comprises the first compound, and a total content of the firstcompound is not less than 1 part by mass and not more than 45 parts bymass based on 100 parts by mass of the base resin.
 3. Theradiation-sensitive resin composition according to claim 1, wherein amolecular weight of an anionic moiety in the radiation-sensitive acidgenerator is 230 or more.
 4. A method of forming a resist pattern,comprising: forming a resist film from the radiation-sensitive resincomposition according to claim 1; exposing the resist film; anddeveloping the exposed resist film.
 5. The radiation-sensitive resincomposition according to claim 1, wherein the acid diffusion controllingagent is an onium salt compound wherein the onium salt compound isdegraded and loses acid diffusion controlling properties by an exposure.6. The radiation-sensitive resin composition according to claim 5,wherein the onium salt compound is triphenylsulfonium salicylate ortriphenylsulfonium 10-camphorsulfonate.
 7. The radiation-sensitive resincomposition according to claim 1, wherein Z₁ ⁺, Z₂ ⁺, and Z₃ ⁺ are eachindependently represented by formula (X-1):

wherein: k1, k2 and k3 are each independently an integer of 0 to 5; andR^(a1), R^(a2) and R^(a3) are each independently, at each occurrence, asubstituted or unsubstituted, straight or branched chain alkyl group,alkoxy group or alkoxycarbonyloxy group having a carbon number of 1 to12; a substituted or unsubstituted, monocyclic or polycyclic cycloalkylgroup having a carbon number of 3 to 12; a substituted or unsubstitutedaromatic hydrocarbon group having a carbon number of 6 to 12; a hydroxygroup; —OSO₂—R^(P); —SO₂—R^(Q); or —S—R^(T), wherein R^(P), R^(Q) andR^(T) are each independently, at each occurrence, a substituted orunsubstituted, straight or branched chain alkyl group having a carbonnumber of 1 to 12; a substituted or unsubstituted alicyclic hydrocarbongroup having a carbon number of 5 to 25; or a substituted orunsubstituted aromatic hydrocarbon group having a carbon number of 6 to12.
 8. The radiation-sensitive resin composition according to claim 1,wherein the monovalent onium cation represented by Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺is an unsubstituted triphenylsulfonium.
 9. The method according to claim4, wherein the radiation-sensitive acid generator comprises the firstcompound, and a total content of the first compound is not less than 1part by mass and not more than 45 parts by mass based on 100 parts bymass of the base resin.
 10. The method according to claim 4, wherein amolecular weight of an anionic moiety in the radiation-sensitive acidgenerator is 230 or more.
 11. The method according to claim 4, whereinthe acid diffusion controlling agent is an onium salt compound whereinthe onium salt compound is degraded and loses acid diffusion controllingproperties by an exposure.
 12. The method according to claim 11, whereinthe onium salt compound is triphenylsulfonium salicylate ortriphenylsulfonium 10-camphorsulfonate.
 13. The method according toclaim 4, wherein Z₁ ⁺, Z₂ ⁺, and Z₃ ⁺ are each independently representedby formula (X-1):

wherein: k1, k2 and k3 are each independently an integer of 0 to 5; andR^(a1), R^(a2) and R^(a3) are each independently, at each occurrence, asubstituted or unsubstituted, straight or branched chain alkyl group,alkoxy group or alkoxycarbonyloxy group having a carbon number of 1 to12; a substituted or unsubstituted, monocyclic or polycyclic cycloalkylgroup having a carbon number of 3 to 12; a substituted or unsubstitutedaromatic hydrocarbon group having a carbon number of 6 to 12; a hydroxygroup; —OSO₂—R^(P); —SO₂—R^(Q); or —S—R^(T), wherein R^(P), R^(Q) andR^(T) are each independently, at each occurrence, a substituted orunsubstituted, straight or branched chain alkyl group having a carbonnumber of 1 to 12; a substituted or unsubstituted alicyclic hydrocarbongroup having a carbon number of 5 to 25; or a substituted orunsubstituted aromatic hydrocarbon group having a carbon number of 6 to12.
 14. The method according to claim 4, wherein the monovalent oniumcation represented by Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ is an unsubstitutedtriphenylsulfonium.
 15. A radiation-sensitive resin composition,comprising: a resin comprising a structure unit having an acid-dissociable group, a content of the structural unit in the base resin being30-75 mol %; a radiation-sensitive acid generator; an acid diffusioncontrolling agent; a fluorine-containing resin having higher content bymass of fluorine atoms than the base resin; and a solvent which is atleast one solvent selected from the group consisting of iso-propanol,4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol,furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, ethyleneglycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol,diethylene glycol, dipropylene glycol, triethylene glycol, tripropyleneglycol, a partially etherized polyhydric alcohol-based solvent in whicha part of hydroxy groups in the polyhydric alcohol is etherized, anether-based solvent, acetone, butanone, methyl-iso-butyl ketone,cyclopentanone, cyclohexanone, methylcyclohexanone, 2,4-pentanedione,acetonylacetone, acetophenone, an amide-based solvent, an ester-basedsolvent, and a hydrocarbon-based solvent, wherein theradiation-sensitive acid generator comprises: a second compound which isat least one compound selected from the group consisting of a compoundrepresented by formula (2-1), a compound represented by formula (2-2), acompound represented by formula (2-3), a compound represented by formula(2-4), a compound represented by formula (2-5), a compound representedby formula (2-7), a compound represented by formula (2-8), a compoundrepresented by formula (2-9), a compound represented by formula (2-10),and a compound represented by formula (2-12); a third compound which isat least one compound selected from the group consisting of a compoundrepresented by formula (3-3), a compound represented by formula (3-5), acompound represented by formula (3-7), a compound represented by formula(3-8), a compound represented by formula (3-9), and a compoundrepresented by formula (3-10); and optionally, a first compoundrepresented by formula (1):

wherein: R¹ is a group having a cyclic structure; X¹¹ and X¹² are eachindependently a hydrogen atom, a fluorine atom, or a fluorinatedhydrocarbon group, provided that at least one of X¹¹ and X¹² is not ahydrogen atom, and at least one of X²¹ and X²² is not a hydrogen atom;A¹¹ and A¹² are each independently a hydrogen atom, or a hydrocarbongroup having a carbon number of 1 to 20; m¹ is an integer of 0 to 5; n¹is an integer of 1 to 4; G is a single bond, or a divalent linkinggroup; and Z₁ ⁺, Z₂ ⁺ and Z₃ ⁺ are each independently a monovalent oniumcation, wherein an amount of the radiation-sensitive acid generator isfrom 7 to 35 mass parts with respect to 100 mass parts of the baseresin, an amount of the acid diffusion controlling agent is from 5 to110 mass parts with respect to 100 mass parts of the radiation-sensitiveacid generator, and an amount of the fluorine-containing resin is from 1to 5 mass parts with respect to 100 mass parts of the base resin. 16.The radiation-sensitive resin composition according to claim 1, whereinan amount of the second compound is 5 mass parts or more with respect to100 mass parts of the base resin, and an amount of the third compound is5 mass parts or more with respect to 100 mass parts of the base resin.17. The radiation-sensitive resin composition according to claim 1,wherein the amount of the acid diffusion controlling agent is from 4 to7 mass parts with respect to 100 mass parts of the base resin.
 18. Theradiation-sensitive resin composition according to claim 1, wherein theradiation-sensitive resin composition consists of: the base resin; theradiation-sensitive acid generator; the acid diffusion control agent;the fluorine-containing resin; optionally a surfactant; and optionally asensitizer.
 19. The radiation-sensitive resin composition according toclaim 1, wherein an amount of the second compound is 5 mass parts ormore with respect to 100 mass parts of the base resin, an amount of thethird compound is 5 mass parts or more with respect to 100 mass parts ofthe base resin, and the amount of the acid diffusion controlling agentis from 4 to 7 mass parts with respect to 100 mass parts of the baseresin.
 20. The radiation-sensitive resin composition according to claim15, wherein an amount of the second compound is 5 mass parts or morewith respect to 100 mass parts of the base resin, an amount of the thirdcompound is 5 mass parts or more with respect to 100 mass parts of thebase resin, and the amount of the acid diffusion controlling agent isfrom 4 to 7 mass parts with respect to 100 mass parts of the base resin.